A direct and sensitive electrochemical sensing platform based on ionic liquid functionalized graphene nanoplatelets for the detection of bisphenol A

A simple electrochemical sensor for bisphenol A (BPA) was developed based on a composite of graphene nanoplatelets (GNPs) and 1-butyl-2, 3-dimethylimidazolium tetrafluoroborate (ionic liquid, IL) as a modifier for glassy carbon paste electrodes (GCPEs). Scanning electron (SEM) and atomic force microscopy (AFM) were employed to characterize the morphology and surface modification. The electrochemical behavior of BPA on IL-GNP/GCPEs was investigated and the results showed that IL-GNP composites enhance the electrochemical signal toward BPA due to the synergetic effect of GNPs and IL. The experimental parameters including the amount of IL and GNPs, pH of solution, pulse potential, step potential, and scan rate were optimized. Under optimal conditions, the proposed sensor exhibited a linear relationship between signal and BPA concentrations ranging from 0.02–5.0 μM, with detection and quantification limits of 6.4 nM and 0.02 μM respectively. Moreover, the electrochemical sensor showed good repeatability (RSD = 3.3%, n = 5 measurements), good reproducibility (RSD = 3.8%, n = 5 sensors), high accuracy of 95.3–104.5% recovery, acceptable selectivity, and stability. The sensor was successfully applied to the determination of BPA in water samples in contact with plastic materials. The results were satisfactory and in agreement with reference values from a standard HPLC method. © 201

Coumarin Probe for Selective Detection of Fluoride Ions in Aqueous Solution and Its Bioimaging in Live Cells

We have synthesized novel coumarin-based fluorescent chemosensors for detection of fluoride ions in aqueous solution. The detection mechanism relied on a fluoride-mediated desilylation triggering fluorogenic reaction and a strong interaction between fluoride and the silicon center. In this work, the hydroxyl-decorated coumarins containing oxysilyl moiety have been synthesized through the aldehyde-functionalized coumarins. The optical responses toward fluoride, as well as aqueous stability studies of both aldehyde and hydroxyl functionalized coumarins, have been investigated. Due to the highest fluorescence enhancement upon the addition of fluoride and good stability in aqueous solution, the hydroxyl-decorated coumarin connected with the bulky tert-butyldiphenyloxysilyl group (-OSitBuPh2) has been selected for further investigation of its potential as a fluoride sensor. This hydroxyl-decorated coumarin can selectively sense fluoride ions in aqueous media (contain 0.8% MeCN) with desirable response times (40 min). The limit of detection of this compound was determined as 0.043 ppm, satisfying the standard fluoride level (0.7 ppm) in drinking water recommended by U.S. Department of Health and Human Services. The application of this silyl-capped coumarin derivative for fluoride analysis in collected water samples displayed satisfactory analytical accuracy (<5% error). Finally, this compound was successfully employed in fluorescence bioimaging of fluoride ions in human liver cancer cells, indicating its excellent cell permeability, ability to retain inside the living cells, and good stability under physiological conditions

A novel ditopic receptor and reversal of anion binding selectivity in the presence and absence of bound cation

A calix[4]arene-derived ditopic receptor 1 has been synthesized. In the absence of Na+, the receptor binds acetate in preference to diphenyl phosphate (as the tetrabutylammonium salts), but in the presence of Na+, the selectivity is reversed and the receptor, instead, binds diphenyl phosphate, and not acetate, which preferentially forms a salt ion-pair in free solution

Synthesis of Copper-Chelates Derived from Amino Acids and Evaluation of Their Efficacy as Copper Source and Growth Stimulator for <i>Lactuca sativa</i> in Nutrient Solution Culture

Five tetradentate ligands were synthesized from l-amino acids and utilized for the synthesis of <b>Cu­(II)-chelates 1</b>–<b>5</b>. The efficacy of Cu­(II)-chelates as copper (Cu) source and growth stimulator in hydroponic cultivation was evaluated with <i>Lactuca sativa</i>. Their stability test was performed at pH 4–10. The results suggested that <b>Cu­(II)-chelate 3</b> is the most pH tolerant complex. Levels of Cu, Zn, and Fe accumulated in plants supplied with Cu­(II)-chelates were compared with those supplied with CuSO₄ at the same Cu concentration of 8.0 μM. The results showed that <b>Cu­(II)-chelate 3</b> significantly enhanced Cu, Zn, and Fe content in shoot by 35, 15, and 48%, respectively. Application of <b>Cu­(II)-chelate 3</b> also improved plant dry matter yield by 54%. According to the results, <b>Cu­(II)-chelate 3</b> demonstrated the highest stimulating effect on plant growth and plant mineral accumulation so that it can be used as an alternative to CuSO₄ for supplying Cu in nutrient solutions and enhancing the plant growth

Efficiency of SPIONs functionalized with polyethylene glycol bis (amine) for heavy metal removal

Hybrid magnetic nanoparticles based on poly(methylmethacrylate) (PMMA) and super-paramagnetic iron oxide nanopaticles (SPIONs) with selective surface modification has been developed for heavy metal removal by applying external magnetic fields. The nanoparticles were prepared by the emulsion polymerization technique in an aqueous suspension of SPIONs. The hydrolysis of carboxyl functional group was then applied for grafting polyethylene glycol bis(amine)(PEG-bis(amine)) onto the PMMA-coated SPIONs. The morphology, the chemical structure and the magnetic properties of the grafted nano particles were investigated. The efficiency of the hybrid nanoparticles for heavy metal removal were conducted on Pb(II), Hg(II), Cu(II) and Co(II) in aqueous solutions. The metal concentration in the solutions after separation by the hybrid nanoparticles was determined by inductively coupled plasma optical emission spectrometer (ICP-OES). The results show the heavy metal uptake ratios of 0.08, 0.04, 0.03, and 0.01 mM per gramme of the grafted SPIONs for Pb(II), Hg(II), Cu(II), and Cu(II), respectively. A competitive removal of Cu(II), Pb(II), Co(II) and Hg(II) ions in mixed metal salt solutions has also been studied. The heavy metal removal efficiency of the hybrid nanoparitcles was found to depend on the cation radius, in accordance with capture of metal ions by the amine group. (C) 2016 Elsevier B.V. All rights reserved

A direct and sensitive electrochemical sensing platform based on ionic liquid functionalized graphene nanoplatelets for the detection of bisphenol A

A simple electrochemical sensor for bisphenol A (BPA) was developed based on a composite of graphene nanoplatelets (GNPs) and 1-butyl-2, 3-dimethylimidazolium tetrafluoroborate (ionic liquid, IL) as a modifier for glassy carbon paste electrodes (GCPEs). Scanning electron (SEM) and atomic force microscopy (AFM) were employed to characterize the morphology and surface modification. The electrochemical behavior of BPA on IL-GNP/GCPEs was investigated and the results showed that IL-GNP composites enhance the electrochemical signal toward BPA due to the synergetic effect of GNPs and IL. The experimental parameters including the amount of IL and GNPs, pH of solution, pulse potential, step potential, and scan rate were optimized. Under optimal conditions, the proposed sensor exhibited a linear relationship between signal and BPA concentrations ranging from 0.02–5.0 μM, with detection and quantification limits of 6.4 nM and 0.02 μM respectively. Moreover, the electrochemical sensor showed good repeatability (RSD = 3.3%, n = 5 measurements), good reproducibility (RSD = 3.8%, n = 5 sensors), high accuracy of 95.3–104.5% recovery, acceptable selectivity, and stability. The sensor was successfully applied to the determination of BPA in water samples in contact with plastic materials. The results were satisfactory and in agreement with reference values from a standard HPLC method. © 201

Odd–Even and Hydrophobicity Effects of Diacetylene Alkyl Chains on Thermochromic Reversibility of Symmetrical and Unsymmetrical Diyndiamide Polydiacetylenes

Two series of symmetrical (<b>S<i>x</i></b>) and unsymmetrical (<b>U<i>y</i></b>) diacetylene monomers containing diamide groups with different methylene units are successfully prepared. Photopolymerization of their nanovesicles dispersed in water is carried out by irradiation at 254 nm affording blue sols of the corresponding PDAs. The degree of thermochromic reversibility (%DR) of the PDA sols are determined using UV–vis spectroscopy in order to probe effects of the number of the methylene units, <b><i>x</i></b> and <b><i>y</i></b>, within the linker and hydrophobic tail, respectively. The complete color reversibility (%DR > 89%) is observed only when <b><i>x</i></b> is an even number while partially reversible or irreversible thermochromism (%DR < 65%) is displayed in the case of odd <b><i>x</i></b> number. For the <b>U<i>y</i></b> series, the color recovering ability within the heating and cooling process increases along with the <b><i>y</i></b> number; %DR = 3, 62, and 90% for <b><i>y</i></b> = 0, 4, and 16, respectively. This work is the first direct demonstration of the roles of number of methylene units within the diacetylene monomers on the thermochromic reversibility of their PDAs that provide additional dimensions for rational molecular design in the development of PDA thermal sensors

Inclusion Complexes between Amphiphilic Phenyleneethynylene Fluorophores and Cyclodextrins in Aqueous Media

Binding events of cyclodextrins (CyD's) in aqueous media are important for designing and explaining the host–guest chemistry applied in sensing and controlled release systems. A water-soluble tricationic compound (<b>3N</b>^<b>+</b>) with three branches of phenyleneethynylene fluorescent moieties and its related amphiphilic compounds (<b>3C</b>^<b>‑</b>, <b>N</b>^<b>0</b><b>N</b>^<b>+</b>, <b>N</b>^<b>+</b>, and <b>2N</b>^<b>+</b>) are employed as molecular probes in the systematic characterization of the supramolecular interactions with CyD's (α, β, and γ). The strong fluorescence enhancement, combined with induced circular dichroism (CD) signals and ¹H NMR data, is evidence of 1:1 static inclusion complexes of <b>3N</b>^<b>+</b>/γ-CyD and <b>2N</b>^<b>+</b>/γ-CyD. <b>3N</b>^<b>+</b> presents a structural design which can form inclusion complexation with γ-CyD with one of the highest binding constants of 3.0 × 10⁴. The relatively moderate fluorescence enhancement, shift of ¹H NMR signals, and weak induced CD signals indicate fast exchange complexation of β-CyD with the amphiphilic guest molecules. The interaction with α-CyD is perceived only for <b>N</b>^<b>0</b><b>N</b>^<b>+</b>, the only nonbranched fluorescent guest model, via its strong fluorescence enhancement. However, the lack of ¹H NMR signal splitting and the lack of induced CD signals suggest the noninclusion mode of binding between <b>N</b>^<b>0</b><b>N</b>^<b>+</b> and α-CyD

Reusability, Long‐Life Storage and Highly Sensitive Zirconium Nitride (ZrN) Surface‐Enhanced Raman Spectroscopy (SERS) Substrate Fabricated by Reactive Gas‐Timing Rf Magnetron Sputtering

Abstract Transition metal nitrides (TMN) are promising material alternative to replace noble metals in the field of plasmonic applications, especially surface‐enhanced Raman spectroscopy (SERS). Here  we  demonstrate a practical surface enhanced Raman spectroscopy (SERS) substrate using zirconium nitride (ZrN) thin films grown by reactive gas‐timing (RGT) rf magnetron sputtering. The tailored properties of ZrN thin film exploited for SERS activity could be achieved to obtain a highly sensitive ZrN thin film SERS substrate with the enhancement factor (EF) of 1.24 × 106 and 4.8 %RSD at 1626 cm‐1 toward methylene blue (MB) analyte which are comparable to the optimized Au sputtered thin films (EF=1.18 × 106 and with 5.1%RSD).  We  find that the spatial plasmonic hotspots on the surface of ZrN SERS substrate controlled by the turn‐on timing of Ar:N2 sputtered gas sequence, leading to the discrete conductive surface profile, strongly relates to non‐stoichiometric composition and the degree of (200)‐oriented texture at the surface of ZrN thin film. Furthermore, ZrN thin film SERS substrates exhibit an excellent recyclability more than 30 cycles with simple cleaning process and a storage time longer than 6 months. The detection and reusability of ZrN SERS substrate on the low concentration of trinitrotoluene (TNT) for homeland security are also performed