A novel Cr3+ turn-on probe based on naphthalimide and BINOL framework

Colorimetric detection of Cr3+ in dietary supplements using a smartphone based on EDTA and tannic acid-modified silver nanoparticles

A simplistic, portable and low-cost method for the rapid detection of Cr³⁺ was developed based on a smartphone readout and a co-functionalized silver nanoparticles (AgNPs) system for use as an on-site device in resource-poor areas. The presence of Cr³⁺ induced aggregation of AgNPs through coordinated complex formation between Cr³⁺ and stabilizing agents on the NPs surface, resulted in a bright yellow of an AgNPs solution turned to wine red along with a SPR band was red-shifted from 429 nm to 625 nm. A smartphone with an available free application, called "PhotoMetrix" was used to measure the RGB (red, green, blue) values of the color intensities in the AgNPs system and convert into Cr³⁺ concentration by using univariate calibration curves in less than 60s. This smartphone-based detection system showed a high selectivity of AgNPs with Cr³⁺ and gave a positive coefficient correlation (R² = 0.9878) between the intensity of channel R and the Cr³⁺ concentration, with a linear range of 2.0-5.0 mg L^-1, and a detection limit of 1.52 mg L^-1. Furthermore, the proposed method has been successfully applied for quantification of Cr³⁺ in dietary supplement samples. The results obtained were in close agreement with those obtained in FAAS (Flame Atomic Absorption Spectrometry). The developed colorimetric system based on a smartphone readout device exhibits feasibility and reliability for on-site Cr³⁺ detection in the real samples.

Preparation of anthracene-based tetraperimidine hexafluorophosphate and selective recognition of chromium(III) ions

A novel anthracene-based tetraperimidine hexafluorophosphate 3 was prepared, and its structure was determined through X-ray analysis, HRMS as well as ¹H and ¹³C NMR spectroscopy. In the cationic moiety of 3, two (N-ethylperimidinyl–C₂H₄)₂NCH₂– arms were attached to the 9- and 10-positions of anthracene. In addition, compound 3 was used as a chemosensor to research the ability to recognize Cr³⁺ through fluorescence and UV titrations, HRMS, as well as ¹H NMR and IR spectroscopy. The results indicate that 3 is an effective chemosensor for Cr³⁺.

Fabrication of silver nanoclusters with enhanced fluorescence triggered by ethanol solvent: a selective fluorescent probe for Cr3+ detection

We present a facile method for the preparation of red-emitting and water-soluble silver nanoclusters (Ag NCs) using dihydrolipoic acid and sodium borohydride as the template and reducing agent. Ethanol solvent is demonstrated to endow Ag NCs with dramatically enhanced fluorescence; therefore, the Ag NCs are synthesized in ethanol/water solution (e/w-Ag NCs) instead of aqueous solution. Specific trivalent chromium (Cr³⁺) recognition capability of the e/w-Ag NCs can thus be obtained on the basis of its fluorescence quenching. The mechanisms for fluorescence enhancement and quenching of the e/w-Ag NCs triggered by ethanol and Cr³⁺, respectively, are investigated in detail. Next, a fluorescence method for detection of Cr³⁺ is established and its analytical performance is evaluated: the detection limit for Cr³⁺ is 0.71 μM and the linear range is from 2 to 40 μM. The fluorescent probe exhibits sufficient sensitivity and good selectivity toward Cr³⁺, illustrating that it has great promise for practical application in Cr³⁺ detection.

Potentially toxic elements and environmentally-related pollutants recognition using colorimetric and ratiometric fluorescent probes

A safer detection or sensing of toxic pollutants is one among several environmental contamination issues, across the globe. The ever-increasing industrial practices and controlled or uncontrolled release of toxic pollutants from various industrial sectors is a key source of this environmental problem. Significant research efforts have been or being made to tackle this problematic issue to fulfill the growing needs of the modern world. Despite many useful aspects, heavy metals are posing noteworthy toxicological concerns and human-health related issues at various levels of the ecosystem. In this context, notable efforts from various regulatory authorities, the increase in the concentration of these toxic heavy metals in the environment is of serious concern, so real-time monitoring is urgently required. Herein, we reviewed fluorescent sensor based models and their potentialities to address the detection fate of hazardous pollutants including chromium, manganese, cobalt, nickel, copper, and zinc as model elements. The novel aspects of turn-on/off fluorescent sensors have also been discussed from a state of the art viewpoint. In summary, comprehensive literature regarding fluorescent sensor based models and their potentialities to detect various types of toxic pollutants is reviewed.

A highly selective colorimetric and fluorescent turn-on chemosensor for Al(3+) based on naphthalimide derivative

A new chemosensor L based on the naphthalimide moiety was synthesized and characterized. L exhibited the high selectivity and sensitivity for Al(3+) in CH3OH, along with colorimetric and fluorometric dual-signaling responses based on the joint contribution of the ICT and CHEF processes. A 1:1 stoichiometry for the L-Al(3+) complex was formed with an association constant of 7.6×10(4)M(-1), and the limit of detection for Al(3+) was determined as 6.9μM. In addition, L was successfully applied to the determination of Al(3+) in real water samples.

Development of a Cr(iii) ion selective fluorescence probe using organic nanoparticles and its real time applicability

Recognition of Cr(iii) ion using highly selective fluorescent organic nanoparticles N1 and its validation using DFT geometry optimization.

A fluorescence on–off sensor for Cu2+and its resultant complex as an off–on sensor for Cr3+in aqueous media

A coumarin–quinoline based fluorescence “on–off–on” sensor detects Cu²⁺and Cr³⁺in aqueous media and MCF-7 cells.

Fluorescent, MRI, and colorimetric chemical sensors for the first-row d-block metal ions

Transition metals (d-blocks) are recognized as playing critical roles in biology, and they most often act as cofactors in diverse enzymes; however, improper regulation of transition metal stores is also connected to serious disorders. Therefore, the monitoring and imaging of transition metals are significant for biological research as well as clinical diagnosis. In this article, efforts have been made to review the chemical sensors that have been developed for the detection of the first-row d-block metals (except Cu and Zn): Cr, Mn, Fe, Co, and Ni. We focus on the development of fluorescent sensors (fall into three classes: "turn-off", "turn-on", and ratiometric), colorimetric sensors, and responsive MRI contrast agents for these transition metals (242 references). Future work will be likely to fill in the blanks: (1) sensors for Sc, Ti, and V; (2) MRI sensors for Cr, Mn, Co, Ni; (3) ratiometric fluorescent sensors for Cr(6+), Mn(2+), and Ni(2+), explore new ways of sensing Fe(3+) or Cr(3+) without the proton interference, as well as extend applications of MRI sensors to living systems.

Selectively sensing first-row transition metal ions through fluorescence enhancement

Fluorescence signaling systems that give enhancement in the presence of first-row transition metal ions are discussed.