Cadmium (II) sensing utilizing three-dimensional graphene/polypyrrole oxides was applied and evaluated for the environmentally relevant analytes. Driven by the need to detect trace Cd (II), we prepared a porous graphene oxide-polypyrrole (pGO/PPy) polymer nanocomposite modified sensor for electrochemical trace analysis of Cd (II). The pGO/PPy was prepared by polypyrrole wrapped with graphene oxide using ultrasound-assisted polymerization and graphene oxide functionalized with carboxyl, which was modified on the sensing electrode for pre-concentration and enhanced the absorption of heavy metal ions. Three-dimension graphene oxide and interconnected porous structure of polypyrrole were fabricated by electro-polymerization and sonication to enhance the preconcentration factors and the sensitivity for cadmium determination. The cadmium sensor fabricated with pGO/PPy nanocomposite displayed a displayed a considerable sensitivity within the linear range from 1μg • L −1 to 100 μg • L −1 , a detection limit of 0.05 μg • L −1 2-orders-lower cadmium than the WHO standard limit. The cadmium sensor could be applied in tap, pond and river water with a high selectivity minimizing electroactive, interfering ions.
Unprecedented interheteromacrocyclic
hosts charge transfer (CT)
crystals were generated by cooling organic solutions containing p-dimethoxybenzene-constituted pillar[5]arene (P5A) and p-benzoquinone-constituted pillar[5]quinone
(P5Q). Despite the weak CT interaction known between p-dimethoxybenzene and p-benzoquinone and
the lack of formation of CT complexes between P5A and P5Q in the solution phase, CT cocrystals between P5A and P5Q were formed with solvent molecules included
into the hosts’ cavities. Such a cocrystallization arises from
an elegant synergy between the CT interaction and solvent-binding-promoted
crystallization. The interhetero hosts CT crystals were studied by
optical and electron microscopic techniques, X-ray powder diffraction,
solid-state NMR, UV–vis, IR spectroscopic studies, and X-ray
single-crystal studies. The solvent complexation was critical for
formation of the supramolecular CT microcrystals. The CT absorption
bands faded upon removing the solvent molecules under vacuum, but
they could be recovered by reuptake of the solvent molecules. Intriguingly,
the CT absorption bands and uptake kinetics are distinguishably different
for various organic solvents, thus providing a unique way to distinguish
between different commonly used chemicals.
Two superaromatic terpyridine ligands (1 and 2) incorporating a corannulene unit at the 4'-position are reported. The optical and metal sensing properties of both ligands were investigated by the naked eye, and UV-vis and fluorescence spectroscopy in this work. In 1, the corannulene motif is directly connected to the 4'-phenylterpyridine domain, while in 2, the corannulene motif and the 4'-phenylterpyridine domain are separated by an acetylene linker. Both 1 and 2 can work as chemosensors for metal ions and display different optical responses to various metal ions. It is shown that both ligands exhibit a colorimetric sensing ability for Fe(2+) through an obvious color change from colorless to magenta, and this color change can be observed easily by the naked eye. The addition of Fe(2+) also leads to significant changes in the absorption spectra of the ligands. A characteristic red shift in the emission spectra is observed in the presence of Zn(2+), which facilitates the discrimination of Zn(2+) from other metal ions. In addition, density functional theory (DFT) and time-dependent-density functional theory (TD-DFT) calculations were performed and shown to be consistent with the observed experimental results.
We have developed a novel mediated biochemical oxygen demand (BOD) biosensor based on immobilized Bacillus subtilis (B. subtilis) on three-dimensional (3D) porous graphene-polypyrrole (rGO-PPy) composite. The 3D porous rGO-PPy composite was prepared using hydrothermal method following with electropolymerization. Then the 3D porous rGO-PPy composite was used as a support for immobilizing negatively charged B. subtilis denoted as rGO-PPy-B through coordination and electrostatic interaction. Further, the prepared rGO-PPy-B was used as a microbial biofilm for establishing a mediated BOD biosensor with ferricyanide as an electronic acceptor. The indirect determination of BOD was performed by electrochemical measuring ferrocyanide generated from a reduced ferricyanide mediator using interdigited ultramicroelectrode array (IUDA) as the working electrode. The experimental results suggested a good linear relationship between the amperometric responses and BOD standard concentrations from 4 to 60 mg/L, with a limit detection of 1.8 mg/L (S/N ≥ 3). The electrochemical measurement of real water samples showed a good agreement with the conventional BOD5 method, and the good anti-interference as well as the long-term stability were well demonstrated, indicating that the proposed mediated BOD biosensor in this study holds a potential practical application of real water monitoring.
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