A switch-on xanthene-triphenylamine based fluorescent and colorimetric sensor for the detection of ultra-trace Hg2+ in food samples and living cells

A novel colorimetric and fluorescent "switch-on" probe based on xanthene-triphenylamine was developed for detection of Hg2+, which threatens public health, food safety and the environment. The probe displayed superior colorimetric and fluorescent selectivity/sensitivity toward Hg2+ over a series of metal ions via Hg2+-triggered deprotection reaction. Hg2+ induced a ∼18-fold enhancement in emission intensity of probe TXS with yellow fluorescence (λem = 558 nm) and led to distinct color transition from light yellow to blue or yellow under daylight depending on solvent mixture. Detection parameters were optimized and examined for the influence that they exerted on the detection which involved the usage of the Box-Behnken design methodology. The sensing pathway was also examined theoretically by DFT and TD-DFT calculations. The probe was successfully utilized for the detection of Hg2+ in several food and water samples with good recoveries. Cell imaging studies demonstrated that the probe was suitable for Hg2+ detection in live cells.

Red-fluorescent graphene quantum dots from guava leaf as a turn-off probe for sensing aqueous Hg(ii)

In this work, we have prepared red-fluorescent graphene quantum dots and utilized as a highly selective and sensitive fluorescence turn-off probe for detection of the toxic metal ion Hg²⁺ from guava leaf extract.

Fluorescence determination of trace level of cadmium with pyrene modified nanocrystalline cellulose in food and soil samples

Cadmium is one of the most toxic metal that accumulates in the human body via food chain, industrial/agricultural activites. It also has negative effects in organs such as the brain, liver and central nervous system. Therefore, International Agency for Research on Cancer is classified cadmium as "carcinogenic to humans" (group 1). In this work, novel pyrene modified nanocrystalline cellulose (NP-1) was designed as a fluorescence sensor for selective determination of Cd²⁺ in food and soil samples. FTIR, UV-Vis, SEM, TEM and TGA were used for structural, morphological characterizations and thermal properties of NP-1. The experimental conditions such as selectivity, pH, sensor concentration, photostability, time and interaction mechanism were examined and optimized. The LOD was determined as 0.09 μM (10.70 μg/L) which was lower than WHO's permissible limit of cadmium in plant with 0.10-60.00 μM linear working range. Validation of the present method was performed by spike/recovery test and ICP-MS, then fluorescence determination of Cd²⁺ in food and soil samples was succesfully applied. The results indicated that the proposed method based on "turn-on" fluorescence of NP-1 was a simple, sensitive and reliable for rapid determination of Cd²⁺ in real samples with high applicability and stability.

The novel anthracene decorated dendrimeric cyclophosphazenes for highly selective sensing of 2,4,6-trinitrotoluene (TNT)

Novel fluorescent anthracene-decorated cyclotri- and cyclotetraphosphazenes (5 and 6) are designed and synthesized, and their chemosensor behaviors against nitroaromatic compounds are examined by UV/Vis and fluorescence spectroscopies for addressing the sensors with cyclophosphazenes for 2,4,6-trinitrotoluene detection. The fluorescence intensities of (5 and 6) are found to be selectively quenched by only 2,4,6-trinitrotoluene through the non-covalent π⋯π stacking interactions between anthracene-substituted cyclophosphazenes and 2,4,6-trinitrotoluene. In addition, cyclic voltammetry and theoretical calculation of novel sensor systems are studied. The proposed fluorescent sensor systems are critical in terms of practical detection of 2,4,6-trinitrotoluene.

Constitutional isomers of dendrimer-like pyrene substituted cyclotriphosphazenes: synthesis, theoretical calculations, and use as fluorescence receptors for the detection of explosive nitroaromatics

Two constitutionally isomeric bis-pyrenyl phenol dendrons (4 and 6) and their dendrimer-like cyclotriphosphazene derivatives (5 and 7) are designed, synthesized and fluorescence detection behaviors are evaluated for nitro aromatic compounds (NACs).