A novel fluorescent distinguished probe for Cr (VI) in aqueous solution

Highly Dense TiO2 Nanorods as Potential Electrode Material for Electrochemical Detection of Multiple Heavy Metal Ions in Aqueous Medium

This study describes the direct deposition of extremely dense TiO2 nanorods (NRs) on an ITO substrate for the improved detection of heavy metal ions (HMIs). A facile hydrothermal method was employed to synthesize TiO2 NRs on the ITO substrate at ~130 °C. Synthesized TiO2 NRs were analyzed for morphological, structural, and electrochemical properties. As an electrode material, TiO2 NRs were used for the simultaneous detection of three HMIs (i.e., Cr3+, Cu2+, and Hg2+), which showed a remarkably high sensitivity of ~92.2 µA.mM-1.cm-2 for the Cu2+ ion. Relatively low sensitivities of ~15.6 µA.mM-1.cm-2 and ~19.67 µA.mM-1.cm-2 were recorded for the Cr3+ and Hg2+ ions, respectively. The fabricated TiO2 NR-based HMI sensor showed an effective dynamic linear detection range with low LOD values of ~21.7 mM, 37 mM, and ~ 28.5 mM for Cr3+, Cu2+, and Hg2+, respectively. The TiO2 NR-based HMI sensor exhibited efficient charge transfer over the electrode toward the trace detection of Cr3+, Cu2+, and Hg2+. Moreover, the reliability of the TiO2 NR-based HMI sensor was assessed, which exhibited a promising stability of 30 days. The obtained results indicate that TiO2 NRs grown on an ITO substrate are a promising electrode material for detecting hazardous Cr3+, Cu2+, and Hg2+ and might eventually be commercialized in the near future.

An Overview on Coinage Metal Nanocluster-Based Luminescent Biosensors via Etching Chemistry

The findings from the synthetic mechanism of metal nanoclusters yield the etching chemistry based on coinage metal nanoclusters. The utilization of such chemistry as a tool that can alter the optical properties of metal nanoclusters has inspired the development of a series of emerging luminescent biosensors. Compared with other sensors, the luminescent biosensors have the advantages of being more sensitive, saving time and saving cost. We reviewed topics on the luminescent sensors based on the etching of emissive coinage metal nanoclusters. The molecules possessing varied etching ability towards metal nanoclusters were categorized with discussions of corresponding etching mechanisms. The understanding of etching mechanisms favored the discussions of how to use etching methods to detecting biochemical molecules. The emerging luminescent biosensors via etching chemistry also provided challenges and new opportunities for analytical chemistry and sensors.

Intracellular Biotransformation of Cu(II)/Cu(I) Explained High Cu Toxicity to Phytoplankton Chlamydomonas reinhardtii

The toxicity of Cu is related to its redox species, but the differential toxicity of Cu(II) and Cu(I) remains unknown. In the present study, we developed a novel protocol to simultaneously detect the biologically produced extracellular Cu(I) and internalized Cu(II) in a freshwater phytoplankton Chlamydomonas reinhardtii. The intracellular Cu(I) was further imaged using a fluorometric probe. Combining these pieces of evidence, we demonstrated that Cu(I) dominated the Cu toxicity in algal cells under Fe-deficient conditions. Our results showed that the labile Cu(I) content increased significantly in the low Fe quota cells. Intracellular biotransformation from Cu(II) to Cu(I) rather than the direct uptake of Cu(I) was responsible for the high Cu toxicity. The abnormal biotransformation from Cu(II) to Cu(I) under Fe deficiency was not resulted from the increase of overall Cu bioaccumulation but was likely due to the change of Cu(II) metabolism. High contents of Cu(II) were accumulated in the normal cells and the low Zn quota cells upon Cu exposure but did not induce cell death, further suggesting that Cu(I) dominated the Cu toxicity to the algae. This is the first study to simultaneously consider the effect of Cu(I) and Cu(II) during Cu exposure in phytoplankton. The results uncovered the underlying mechanisms of high Cu toxicity under Fe deficiency and highlighted the critical role of modulation of Cu metabolism in phytoplankton.

Facile Synthesis of Luffa Sponge Activated Carbon Fiber Based Carbon Quantum Dots with Green Fluorescence and Their Application in Cr(VI) Determination

Carbon quantum dots (CQDs) were prepared by a chemical oxidation method using luffa sponge based activated carbon fiber as the raw material. The obtained CQDs were well characterized. The fluorescence quenching effect of Cr(VI) ion on CQDs was investigated. The results show that the addition of Cr(VI) changes the intensity of the ultraviolet characteristic absorption peak of CQDs, and causes static quenching of the fluorescence of CQDs. With the increase in the Cr(VI) concentration, the fluorescence of CQDs was gradually extinguished linearly.

Fluorescence-tunable copper nanoclusters and their application in hexavalent chromium sensing

Generally, metal nanoclusters are synthesized using only a single ligand. Thus, the properties and applications of these nanomaterials are limited by the nature of the ligand used. In this study, we have developed a new synthetic strategy to prepare bi-ligand copper nanoclusters (Cu NCs). These bi-ligand Cu NCs are synthesized from copper ions, thiosalicylic acid, and cysteamine by a simple one-pot method, and they exhibit high quantum yields (>18.9%) and good photostability. Most interestingly, the fluorescence intensities and surface properties of the Cu NCs can be tailored by changing the ratio of the two ligands. Consequently, the bi-ligand Cu NCs show great promise as fluorescent probes. Accordingly, the Cu NCs were applied to the inner-filter-effect-based detection of hexavalent chromium in water. A wide linear range of 0.1–1000 μM and a low detection limit (signal-to-noise ratio = 3) of 0.03 μM was obtained. The recoveries for the real sample analysis were between 98.3 and 105.0% and the relative standard deviations were below 4.54%, demonstrating the repeatability and practical utility of this assay.

Generally, metal nanoclusters are synthesized using only a single ligand.

An inner filter effect based Schiff base chemosensor for recognition of Cr(vi) and ascorbic acid in water matrices

An effective and simple fluorescent sensing approach for recognition of Cr(vi) using a Schiff base chemosensor,N′-[(E)-(3,4-dimethoxyphenyl) methylidene] furan-2-carbohydrazide, was developed.

A selective fluorescent 'turn-on' sensor for recognition of Zn(2+) in aqueous media

A new rhodamine-based fluorescent probe 'RhAP' was synthesized and successfully characterized using FT-IR, (13)C NMR and (1)H NMR spectroscopies, LC-MS/MS spectrometry and elemental analysis. The RhAP, a colorless and non-fluorescent compound, showed a selective fluorescent response and colorimetric change for Zn(2+) in HEPES buffer (10mM, EtOH:water, 2:1, v/v, pH7.2). Upon the addition of two equivalents of Zn(2+) to a solution of RhAP, a nearly 35-fold enhancement of the fluorescence intensity, with an emission maximum at 578 nm, was observed in comparison to the sensor alone under the same experimental conditions. The complex formation between RhAP and Zn(2+) was found to have a 1:1 ratio based on calculations obtained from Job's plot and the mole ratio plot methods. The results showed that RhAP can be used as an effective fluorescent probe for selective detecting of Zn(2+) in an aqueous medium.

Ultra-sensitive fluorescence determination of chromium(vi) in aqueous solution based on selectively etching of protein-stabled gold nanoclusters

In this work, we have developed a simple, cost-effective and sensitive fluorescent method for the selective determination of chromium(vi) ions (Cr(vi)) in aqueous solution.

Synthesis and Fe3+ Recognition of Novel Triazole Schiff-Base Derivatives Bearing Fluorogenic Naphthalene and Anthracene Units

Novel triazole Schiff-bases derivatives have been synthesised from 3,5-diaryl-4-amino-1,2,4-triazole with naphthaldehyde and anthraldehyde. The emission spectrum of 3,5-diphenyl-4-(anthrylmethyleneamino)-1,2,4-triazole exhibited fluorescent quenching upon chelation to Fe3+ ions.

A highly selective fluorescent probe for Cu2+ based on rhodamine B derivative

A new fluorescent probe 1 for Cu(2+) based on a rhodamine B derivative was designed and synthesized. Probe 1 displays high sensitivity toward Cu(2+) and about a 37-fold increase in fluorescence emission intensity is observed upon the addition of 10 equiv. Cu(2+) in 50% water/ethanol buffered at pH 7.10. Besides, upon binding Cu(2+) a remarkable color change from colorless to pink was easily observed by the naked eyes. The reversible dual chromo- and fluorogenic response toward Cu(2+) is likely due to the chelation-induced ring-opening of rhodamine spirolactam. The linear response range covers a concentration range of Cu(2+) from 8.0×10(-7) to 1.0×10(-4) mol/L and the detection limit is 3.0×10(-7) mol/L. Except Co(2+), the probe exhibits high selectivity for Cu(2+) over a large number of cations such as alkaline, alkaline earth and transitional metal ions. The accuracy and precision of the method were evaluated by the analysis of the standard reference material, copper in water (1.0 mol/L HNO3). The proposed probe has been used for direct measurement of Cu(2+) content in river water samples and imaging of Cu(2+) in living cells with satisfying results, which further demonstrates its value of practical applications in environmental and biological systems.

Synthesis, Crystal Structure and Fe3+ Recognition of Novel Triazolethione Schiff Base Derivatives

Triazolethione Schiff base derivatives have been synthesised from 3-(3-methyl- 4-amino-5-sulfanylidene-4,5-dihydro-1H-1,2,4-triazol-1-yl)-1,3-diphenylpropan-1-one with aromatic aldehydes (ArCHO) and an X-ray single crystal structure for Ar=Ph has been determined. UV-Vis and fluorescence spectral data indicate that the Schiff base where Ar=2-hydroxynaphthyl can recognise selectively Fe3+ and a 1:1 stoichiometric complex is formed between the receptor and the cation.