Search

Two azo dyes, ( E )-3-(benzo[ d ]thiazol-2-yldiazenyl)-4-hydroxy-2 H -chromen-2-one (3CBD) and ( E )-4-hydroxy-3-(quinolin-2-yldiazenyl)-2 H -chromen-2-one (3CQD), were designed and synthesized using facile methods. The structures were validated through FTIR and NMR spectroscopy. The photophysical property analyses were further studied using UV-Vis and fluorescence spectrophotometers. Consequently, the absorption and emission spectra of 3CBD confirmed its selectivity of Hg 2+ and turn-off response to Fe 3+ . On the other hand, the absorption spectra analysis of 3CQD demonstrated selectivity in the presence of Hg 2+ . The colorimetric investigations demonstrated a significant visual response specifically for Hg 2+ , enabling real-time analysis in the corresponding solutions. The presence of other coexisting metal ions does not interfere with the detection of the target metal ion. The fluorescence studies of the two probes revealed that 3CBD was highly fluorescent, which was significantly quenched by Fe 3+ , upon excitation at 340 nm. Utilizing Job plot analyses, it was determined that the complexes 3CBD-Hg 2+ and 3CQD-Hg 2+ exhibit a binding stoichiometry of 1 : 1. The association constants for these complexes were measured to be 7.48 × 10 5 and 9.12 × 10 5 M -1 , respectively, indicating a strong association between both probes and their respective metal ions. Both chemosensors exhibited comparable limits of detection (LOD) and limits of quantification (LOQ) of 0.03 μM and 0.10 μM, respectively. Reversible studies confirmed that only chemosensor 3CQD could serve as a secondary sensor for EDTA. The theoretical studies calculated using Density Functional Theory (DFT) program at B3LYP/6-31G** (Spartan '10 package) level., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A naphthylthioic-based emissive probe (M) bearing a hydroxyl and amine group was designed and synthesized via a one-step Schiff base reaction process. The probe was characterized spectroscopically using 1 H NMR, UV-Vis and fluorescence spectrophotometers. The probe turned out to be spectroscopically and colorimetrically selective and sensitive to multiple cations and anions. Interestingly, the probe displayed characteristics of excited-state intramolecular proton transfer (ESIPT)-driven dual emissive channels; experiencing fluorescence enhancement upon the molar additions of Al 3+ as well as the anions used, events presumably ascribed to chelation fluorescence enhancement (CHEF), hydrogen bonding and deprotonation effects. Moreover, the fluorometric titration with Hg 2+ resulted in ratiometric spectral behaviors of M, with the disappearance of the peak at 450 nm, concomitant with the appearance of a new peak at 520 nm, distinguished by a clear isosbestic point, the same behaviors exhibited by Sn 2+ and Ag + analytes towards M. The introduction of all other cations used, resulted in fluorescence quenching, attributable to chelation enhanced fluorescence quenching (CHEQ), thereby inhibiting the ESIPT process. The experiments were all carried out in the aqueous environment medium of DMSO-H 2 O (9 : 1) at ambient temperature. Theoretical density functional theory calculations were carried out to gain insight into the interaction of M with cations and anions, and their influence on the HOMO-LUMO energy gaps., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Metal sulphides, including zinc sulphide (ZnS), are semiconductor photocatalysts that have been investigated for the photocatalytic degradation of organic pollutants as well as their activity during the hydrogen evolution reaction and water splitting. However, devising ZnS photocatalysts with a high overall quantum efficiency has been a challenge due to the rapid recombination rates of charge carriers. Various strategies, including the control of size and morphology of ZnS nanoparticles, have been proposed to overcome these drawbacks. In this work, ZnS samples with different morphologies were prepared from zinc and sulphur powders via a facile hydrothermal method by varying the amount of sodium borohydride used as a reducing agent. The structural properties of the ZnS nanoparticles were analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) techniques. All-electron hybrid density functional theory calculations were employed to elucidate the effect of sulphur and zinc vacancies occurring in the bulk as well as (220) surface on the overall electronic properties and absorption of ZnS. Considerable differences in the defect level positions were observed between the bulk and surface of ZnS while the adsorption of NaBH 4 was found to be highly favourable but without any significant effect on the band gap of ZnS. The photocatalytic activity of ZnS was evaluated for the degradation of rhodamine B dye under UV irradiation and hydrogen generation from water. The ZnS nanoparticles photo-catalytically degraded Rhodamine B dye effectively, with the sample containing 0.01 mol NaBH 4 being the most efficient. The samples also showed activity for hydrogen evolution, but with less H 2 produced compared to when untreated samples of ZnS were used. These findings suggest that ZnS nanoparticles are effective photocatalysts for the degradation of rhodamine B dyes as well as the hydrogen evolution, but rapid recombination of charge carriers remains a factor that needs future optimization., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Amakali, Živković, Warwick, Jones, Dunnill, Daniel, Uahengo, Mitchell, Dzade and de Leeuw.)

A ditopic multi-colorimetric probe based on the phenylpridyl-thioic moiety (EN) was synthesized via a Schiff base reaction mechanism and characterized using 1 H NMR and UV-vis spectroscopy. The colorimetric analyses carried out revealed that EN was capable of discriminating between a number of heavy metal cations via coordination induced charge transfer, as well as between anions through hydrogen bonding induced charge transfer, in DMSO-H 2 O (9 : 1). In particular, the ditopic probe could spectrally and colorimetrically recognize the most toxic heavy metal cations of Cd 2+ , Pb 2+ and Hg 2+ , among others, in DMSO-H 2 O. Additionally, EN was selective and sensitive to the presence of CN - , F - , AcO - and H 2 PO 4 - in the same solvent system as cations. The reversibility and reproducibility studies showed that EN exhibited complementary IMP/INH logic functions, based on colour and spectral switching (ON/OFF), modulated by F - /Al 3+ . The real time application of the probe was tested on food grade products to detect the presence of F - in toothpastes and mouthwash dissolved in water, as well as cations in underground water (normally saline), which displayed substantial responses. Thus, EN displayed an excellent scope of response and can thus be developed for real time sensing kits, which could be used instantly in on-field analysis. Theoretical studies were conducted to complement the experimental work., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The photophysical properties of Hexamethylenetetramine ( HMT ) were investigated through physical methods and spectroscopically in dimethyl sulfoxide (DMSO) at ambient temperature. Evidently, HMT turned out as a sensor, selective and sensitive to silver ion (Ag + ) only, among other cations, through colorimetric and fluorometric activities (observable by naked eye) and spectrally, both by UV-Vis and fluorescence spectroscopy. The resulting complex pedant ( HMT-Ag ) is highly responsive to the presence of fluoride ion (F - ) in aqueous soluble DMSO, evidenced by changes in absorption spectra as well as fluorescence quenching, upon addition of the respective ions. Consequently, spectral changes induced by the addition of these ions, were consistently concomitant with colour changes, from colourless to light brown ( HMT-Ag ) to dark brown ( HMT-Ag-F ) in daylight condition, while bright light blue colour (HMT) to dark blue brownish (HMT-Ag) under UV-light conditions. The experimental results were complimented by theoretical studies, which are well within agreement of one another., Competing Interests: The authors declare no conflict of interest., (© 2021 The Author(s).)

A naphthoquinone based colorimetric sensor (N) bearing hydrazone receptors in aqueous media was developed and its recognition properties towards biologically important anions in DMSO-water mixture (9 : 1) were investigated using spectroscopic methods. The hydrazone based receptors showed selectivity towards anions (F - , OH - , CN - and AcO - ), through naked eye observable colour changes, from green to light blue (F - , CN - and AcO - ) and violet (OH - ). The colour changes were concomitant with spectral changes. The sensor could also detect the presence of fluoride ions in commercially available toothpastes, through remarkable colour and spectral changes. In addition, test paper strips prepared from N were able to detect the presence of cyanide (KCN) and hydroxide (NaOH) in tap water. The study was complimented by density functional theory computations to have more insight in the interaction between N and the anions., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)