Highly sensitive "turn-on" fluorescent chemical sensor for trace analysis of Cr3+ using electro-synthesized poly(N-(9-fluorenylmethoxycarbonyl)-l-histidine)

A novel fluorescent "Off-On" probe based on phenanthro[9,10-d]imidazole conjugated polymers (PIPF) for Cr3+ detection with high selectivity and sensitivity

Trivalent chromium (Cr3+) causes serious environmental pollution, degradation of the quality of edible agricultural products and human diseases. A novel phenanthro[9,10-d]imidazole-derived conjugated polymers (PIPF) was obtained from 4-(5,10-dibromo-1H-phenanthro[9,10-d]imidazol-2-yl)phenol and diethyl 4,4'-(2,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-fluorene-9,9-diyl)dibutyrate by Suzuki polymerization reaction, which was reasonably demonstrated by 1H NMR spectroscopy, infrared spectroscopy and quantum chemical calculations. The PIPF exhibits a "turn-on" fluorescence response to Cr3+ in DMSO/H2O (98:2, v/v) with naked-eye detection. The limit of detection for Cr3+ was calculated to be 0.073 μM with a linear range of 3-9 μM. The possible mechanism of the PIPF-based Cr3+ fluorescence "turn-on" sensor is due to the inhibition of the PET process by the coordination of Cr3+ to the hexaalkyl ester carbon chain of PIPF (RCOO-). The high sensitivity, good selectivity, and utility of this sensor indicated that PIPF-based "turn-on" fluorescence sensor is a potential fluorescence application for measuring Cr3+ in environmental samples.

Sensitive Cr3+ sensor based on novel poly(luminol-co-1,8-diaminonaphthalene)/CeO2/MWCNTs nanocomposites

In this study, poly(luminol-co-1,8-diaminonaphthalene) (PLim-DAN) was synthesized and subsequently modified with MWCNTs and CeO2 NPs. The synthesized nanocomposites were analyzed using IR, SEM, TEM, and XRD. Furthermore, a comprehensive set of thermal behavior measurements were taken using TGA/DTG analysis. Next, the electroactivity of the developed nanocomposites was tested as an electrochemical sensor to measure the concentration of Cr3+ ions in phosphate buffers. The GCE adapted with the PLim-DAN/CeO2/CNTs-10% nanocomposite (NC) exhibited the highest current response among the other compositions and copolymers. The fabricated nanocomposite sensor showed high sensitivity, with a value of 19.78 μA μM-1 cm-2, and a low detection limit of 4.80 ± 0.24 pM. The analytical performance was evaluated by plotting a current calibration curve versus the concentration of Cr3+ ions. It was found to be linear (R2 = 0.9908) over the range of 0.1 nM to 0.1 mM, identified as the linear dynamic range (LDR). This electrochemical sensor demonstrated that it could be a useful tool for environmental monitoring by accurately detecting and measuring carcinogenic Cr3+ ions in real-world samples.

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.

Conjugated polymers – a versatile platform for various photophysical, electrochemical and biomedical applications: a comprehensive review

Tuneable properties of conjugated polymers are attractive for use in multiple domains like optical, electronic and biological applications.