A dual colorimetric chemosensor based on Schiff base for highly selective and simultaneous recognition of CN− and Sn2+

A ferrocene-based chemo-dosimeter for colorimetric and electrochemical detection of cyanide and its estimation in cassava flour

A simple chemo-dosimeter VDP2 bearing a ferrocene moiety was designed, synthesized, and characterized, and exhibited both chromogenic and electrochemical responses selectively for CN- in H2O-DMSO (9 : 1, v/v) medium. The probe VDP2 showed an instantaneous color change from colorless to yellow with CN- that can readily be observed visually. The deprotonation of the benzimidazole -NH, followed by nucleophilic addition of CN- to the olefinic C-atom, as evidenced by 1H and 13C NMR titration experiments, caused the colorimetric and electrochemical responses. The mass spectral study, CV, FTIR and Mulliken charges computed well supported the proposed mechanism. The electrochemical limit of detection was calculated to be 72 nM. The results of DFT and TD-DFT calculations suggested that the colorless nature of the probe VDP2 is due to weak intramolecular charge transfer (ICT) transition and the yellow color of the VDP2+CN adduct is due to through-space ICT transition. Above all, the probe could be an ideal candidate for monitoring cyanide in water samples and cassava flour with practical significance. A simple and convenient colorimetric method was developed to determine cyanide content in cassava flour.

Hybrid silica nanoparticles functionalized with pyrazolone-tethered organosilane: Synthesis and application for Sn (II) ion sensing in tap water

Pyrazolone tethered triazole functionalized organosilane and their hybrid silica nanoparticles (HSNPs) have been synthesised for the selective detection of Sn(II) using spectrophotometric techniques. The prepared compounds are characterized by FT-IR, NMR (1H and 13C), XRD, mass spectrometry and FE-SEM spectral analyses. The synthesized hybrid silica nanoparticles gave improved detection limit of 4.3 × 10-8 M and stoichiometry of complex between analyte and probe was found to be 1:1. The association constant calculated for organosilane and their HSNPs came out to be 9.54 × 104 M-1 and 7.47 × 104 M-1 while the presence of other ions showed no interference in the sensing behaviour. The results of the use of this sensing system in tap water facilitate its applicability in real samples with the recovery % more than 98.

Dabcyl as a Naked Eye Colorimetric Chemosensor for Palladium Detection in Aqueous Medium

Industrial activity has raised significant concerns regarding the widespread pollution caused by metal ions, contaminating ecosystems and causing adverse effects on human health. Therefore, the development of sensors for selective and sensitive detection of these analytes is extremely important. In this regard, an azo dye, Dabcyl 2, was synthesised and investigated for sensing metal ions with environmental and industrial relevance. The cation binding character of 2 was evaluated by colour changes as seen by the naked eye, UV-Vis and 1H NMR titrations in aqueous mixtures of SDS (0.02 M, pH 6) solution with acetonitrile (99:1, v/v). Out of the several cations tested, chemosensor 2 had a selective response for Pd2+, Sn2+ and Fe3+, showing a remarkable colour change visible to the naked eye and large bathochromic shifts in the UV-Vis spectrum of 2. This compound was very sensitive for Pd2+, Sn2+ and Fe3+, with a detection limit as low as 5.4 × 10-8 M, 1.3 × 10-7 M and 5.2 × 10-8 M, respectively. Moreover, comparative studies revealed that chemosensor 2 had high selectivity towards Pd2+ even in the presence of other metal ions in SDS aqueous mixtures.

A Fluorescence Turn On-off-on Method for Sensitive Detection of Sn2+ and Glycine Using Waste Eggshell Membrane Derived Carbon Nanodots as Probe

Changes in Sn2+ and glycine levels are relevant to many important physiological procedures in human health. However, investigation of their physiological functions is limited because few versatile methods towards Sn2+ and glycine detection have been developed. In this work, a fluorescence turn on-off-on strategy was firstly constructed for rapid and sensitive detection of Sn2+ and glycine through the specific binding between Sn2+ and glycine. Carbon nanodots (CDs) with a quantum yield of 19.5% were synthesized by utilizing inner film of waste eggshell as carbon source and employed as fluorescent probe. In the presence of Sn2+, the fluorescence of CDs was quenched by Sn2+ via the primary inner filter effect (IFE). However, the binding between Sn2+ and glycine prevented the IFE between Sn2+ and CDs, resulting in fluorescence recovery of CDs. Under optimized conditions, the fluorescent response of CDs displayed good linear relationships with the concentrations of Sn2+ in the range of 10-200 µM and 200-5000 µM, and the limit of detection (LOD) was 2.4 µM. For glycine detection, a good linear relationship was obtained in the concentration range of 5-1000 µM with a low LOD down to 0.76 µM. Moreover, the practicability of the assay was also demonstrated by measuring glycine content in human serum samples. This work provides an economical, green and fast method for biological analysis of Sn2+ and glycine.

A colorimetric and turn-on fluorescent sensor for cyanide and acetate-based Schiff base compound of 2,2'-((1E,11E)-5,8-dioxa-2,11-diazadodeca-1,11-diene-1,12-diyl)bis(4-((E)-phenyldiazenyl)phenol)

A novel Schiff base-based sensor (L) has been designed, synthesized, and developed as a fluorescent and colorimetric sensor for cyanide and acetate. This L exhibited a quick response with rapid sensitivity to CN^- and AcO^- through a remarkable color change from yellow to red which was detectable by the naked eyes. It also sensed CN^- and AcO^- in a fluorescent way via an enhancement in fluorescence intensity. The interaction between L and anions (CN^- and AcO^-) was investigated by using UV-Vis studies, and ¹H NMR titration. The theoretical DFT calculations were also employed to support the results, which displayed good agreement with the experimental value acquisition. As the detection limit for cyanide and acetate were 2.1 × 10^-9 M and 1.7 × 10^-9 M; respectively, low concentrations of these anions could be detectable in the proposed L sensor. In addition, L showed significant reversibility of CN^- detection by using Cu²⁺ as a proper reagent with two different sensing methods including color change and UV-Vis. Last but not least, L could be applied to rapidly detect CN^- in a wide range of pH. As a result, the proposed sensor is promising to identify cyanide and acetate in practical applications in medical, biological, and chemical fields.

Recent advances in tin ion detection using fluorometric and colorimetric chemosensors

The innovation of chemosensors for tin ions (Sn4+/Sn2+) has evolved as a key research topic in recent decades, garnering a lot of attention due to their environmental, industrial and biological importance.

1-Adamantanamine-based triazole-appended organosilanes as chromogenic “naked-eye” and fluorogenic “turn-on” sensors for the highly selective detection of Sn2+ ions

1-Adamantanamine based organosilanes 4a–d have been synthesized and possessed selectivity towards Sn2+ ions only and serve as a colorimetric/fluorimetric dual-channel probe. The turn-on fluorescence has been marked on interaction with Sn2+ ions.

Naked-eye colorimetric and turn-on fluorescent Schiff base sensor for cyanide and aluminum (III) detection in food samples and cell imaging applications

A new efficient Schiff base sensor SB3 for fluorescent and colorimetric "naked-eye" "turn-on" sensing of cyanide anion (CN^-) with excellent sensitivity and selectivity was developed. The 4,4'-(perfluoropropane-2,2-diyl)bisphenol group and two phenyl groups were covalently linked by two C = N bonds to extend the conjugation length. The four hydroxyl groups can improve the water solubility of the SB3 sensor. The SB3 sensor exhibited high specificity towards CN^- by interrupting its intramolecular charge transfer, resulting in a color change and remarkable "turn-on" green fluorescence emission. The sensing mechanism is caused by the nucleophilic addition of CN- toward imine groups of the SB3 sensor, leading to breaks of the conjugation, fluorescent spectral changes, and color change. It was confirmed by ¹H NMR titration and Mass spectra. The detection limits for CN^- and Al³⁺obtained by fluorescence spectrum are 0.80 µM and 0.25 µM, respectively. The SB3 sensor can act as an efficient chemical sensor for detecting the CN^- and Al³⁺ ions under common environmental and physiological conditions (pH 5-12). Besides, the sensor can also detect CN^- in food materials (such as sprouting potatoes and cassava flour) and imaging CN^-in living cells with strong "turn-on" fluorescence at 490 nm. SB3 is an excellent CN^- sensor that exhibits some advantages, including easy synthesis, distinct fluorescence and color change, high selectivity, low detection limit, and good anti-interference ability to analyze solution and food samples, together with fluorescence cell imaging.

Preparation of a new fluorescence nanochemosensor for Sn(II) ions by a modified nanoprecipitation method

A new dialdehyde was designed and synthesized containing naphthalene groups, and then its macrocycle was prepared with 1,4-diaminobuthan. A modified nanoprecipitation method has been reported for the preparation of the nanoparticles. In this method, to obtain nanoparticles with small particle sizes, the nucleation rate was increased with decreasing of the mixing time. The organic nanoparticles were used for turn-off fluorescence response of low concentration of Sn²⁺ ions over cations such as Cs⁺, K⁺, Na⁺, Ba²⁺, Ca²⁺, Mg²⁺, Al³⁺, Pb^2+, Zn²⁺, Cu²⁺, Ni²⁺, Co²⁺, Fe²⁺, Mn²⁺, Ag⁺, Cd²⁺, and Hg²⁺ and ions in aqueous buffer solution. The limit of detection was 5.4 nM.