Synthesis and Photocatalytic Application of Magnetic CoFe2O4/Conjugated Poly(vinyl chloride) Derivative Nanocomposite.

CoFe2O4 has potential for application as a magnetically recoverable visible-light photocatalyst, but its photocatalytic activity is encumbered by the high recombination probability of its photogenerated holes (h+) and electrons (e-). This work was undertaken to boost the photocatalysis of CoFe2O4 through coupling with conjugated poly(vinyl chloride) derivative (CPVC). An easily implementable solvothermal-liquid solid mixing-evaporation of the solvent-pyrolysis method was exploited to synthesize CoFe2O4/CPVC nanocomposites. The photocatalytic capabilities of the products were assessed through photocatalyzing the reduction of Cr(VI) under visible-light (λ > 420 nm). The results demonstrate that the optimal CoFe2O4/CPVC nanocomposite (CoFe2O4/CPVC-2) has markedly heightened photocatalytic activity (3.6 times that of CoFe2O4) and competent reusability and is magnetically recoverable. Furthermore, CoFe2O4/CPVC-2 also shows superior performance toward photocatalytic treatment of the diluted Cr(VI)-containing passivation solution of copper alloys. It is deduced based on the photoelectricity measurement results that the increased photocatalysis of CoFe2O4/CPVC-2 is chiefly attributed to its p-n heterojunction structure, which greatly elevates the h+-e- separation and transfer efficiency. When waste PVC plastic films (replacing the new pure PVC powder) were utilized for the synthesis, the obtained CoFe2O4/CPVC nanocomposite exhibited even better photocatalytic activity (4 times that of CoFe2O4). This work not only has made a new magnetically recoverable, efficient visible-light photocatalyst for decontamination of Cr(VI) in water but also is inspirational for recycling PVC plastic waste to produce high-valued visible-light photocatalysts.

Ratiometric electrochemiluminescence sensing and intracellular imaging of ClO- via resonance energy transfer.

Electrochemiluminescence resonance energy transfer (ECL-RET) is a versatile signal transduction strategy widely used in the fabrication of chem/biosensors. However, this technique has not yet been applied in visualized imaging analysis of intracellular species due to the insulating nature of the cell membrane. Here, we construct a ratiometric ECL-RET analytical method for hypochlorite ions (ClO-) by ECL luminophore, with a luminol derivative (L-012) as the donor and a fluorescence probe (fluorescein hydrazide) as the acceptor. L-012 can emit a strong blue ECL signal and fluorescein hydrazide has negligible absorbance and fluorescence signal in the absence of ClO-. Thus, the ECL-RET process is turned off at this time. In the presence of ClO-, however, the closed-loop hydrazide structure in fluorescein hydrazide is opened via specific recognition with ClO-, accompanied with intensified absorbance and fluorescence signal. Thanks to the spectral overlap between the ECL spectrum of L-012 and the absorption spectrum of fluorescein, the ECL-RET effect is gradually recovered with the addition of ClO-. Furthermore, the ECL-RET system has been successfully applied to image intracellular ClO-. Although the insulating nature of the cell itself can generate a shadow ECL pattern in the cellular region, extracellular ECL emission penetrates the cell membrane and excites intracellular fluorescein generated by the reactions between fluorescein hydrazide and ClO-. The cell imaging strategy via ECL-RET circumvents the blocking of the cell membrane and enables assays of intracellular species. The importance of the ECL-RET platform lies in calibrating the fluctuation from the external environment and improving the selectivity by using fluorescent probes. Therefore, this ratiometric ECL sensor has shown broad application prospects in the identification of targets in clinical diagnosis and environmental monitoring.

Amphiphilic Polymer Ligand-Assisted Synthesis of Highly Luminescent and Stable Perovskite Nanocrystals for Sweat Fluorescent Sensing.

The weak interfacial binding affinities of the inorganic perovskite core with ligands and high density of surface defect states induce the facile detachment of surface ligands from nanocrystals (NCs), resulting in their poor colloidal stability and fluorescence in aqueous. In this work, a powerful ligand engineering strategy was proposed for eliminating the surface defects and aggregation of the NCs. Using an amphiphilic polymer octylamine-modified polyacrylic acid (OPA) as a capping ligand, the as-synthesized CsPbBr3 NCs retain high photoluminescence intensity and stability by the modified ligand-assisted reprecipitation method. The increase in the fluorescence lifetime and NC size could also be observed, and how the NC particle size influences fluorescence lifetime was further studied. In addition, the water stability, photostability, and thermal stability were significantly improved, and the fluorescence of NCs can maintain 80.13% of the original value in water for 15 d. We further validated that the strong binding affinity of OPA and oleylamine ligands with CsPbBr3 NCs leads to a reduction in surface trap states, and a large amount of carboxyl groups of the OPA made the NCs preserve good water solubility. In addition, the OPA has the ability of adjusting the particle size of NCs. Furthermore, a wavelength-shifted colorimetric sensor based on these NCs was constructed for detection of Cl- in sweat, which enables the rapid and visual detection of Cl- with high accuracy and stability. Overall, these CsPbBr3 NCs synthesized by the ligand engineering strategy validated their wide applications in biomedical sensing fields.

Dual Functional Molecular Imprinted Polymer-Modified Organometal Lead Halide Perovskite: Synthesis and Application for Photoelectrochemical Sensing of Salicylic Acid.

This work reports the synthesis of dual functional molecularly imprinted polymer (MIP)-modified organometal lead halide perovskite (CH3NH3PbI3) and its application for photoelectrochemical (PEC) bioanalysis of salicylic acid (SA). Specifically, the CH3NH3PbI3 was encapsulated into the MIPs via a simple thermal polymerization process on the indium tin oxide (ITO) glass, and the as-obtained MIPs/CH3NH3PbI3/ITO electrode was characterized by various techniques, which revealed that the MIPs could not only stabilize CH3NH3PbI3 but also improve the electron-hole separation efficiency of CH3NH3PbI3 under light illumination. In the detection of model analyte SA, the PEC sensor, with numerous amounts of recognition sites to SA, exhibited desirable performance in terms of good sensitivity, selectivity, stability, and feasibility for real sample analysis. This work not only featured the use of MIPs/CH3NH3PbI3 for PEC detection of SA but also provided a new horizon for the design and implementation of functional polymers/perovskite materials in the field of PEC sensors and biosensors.

(110)-oriented ZIF-8 thin films on ITO with controllable thickness.

(110)-oriented zeolitic imidazolate framework (ZIF)-8 thin films with controllable thickness are successfully deposited on indium tin oxide (ITO) electrodes at room temperature. The method applied uses 3-aminopropyltriethoxysilane (APTES) in the form of self-assembled monolayers (SAMs), followed by a subsequent adoption of the layer-by-layer (LBL) method. The crystallographic preferential orientation (CPO) index shows that the ZIF-8 thin films are (110)-oriented. A possible mechanism for the growth of the (110)-oriented ZIF-8 thin films on 3-aminopropyltriethoxysilane modified ITO is proposed. The observed cross-sectional scanning electron microscopy (SEM) images and photoluminescent (PL) spectra of the ZIF-8 thin films indicate that the thickness of the ZIF-8 layers is proportional to the number of growth cycles. The extension of such a SAM method for the fabrication of ZIF-8 thin films as described herein should be applicable in other ZIF materials, and the as-prepared ZIF-8 thin films on ITO may be explored for photoelectrochemical applications.

Hidden Order of Boolean Networks.

It is a common belief that the order of a Boolean network is mainly determined by its attractors, including fixed points and cycles. Using the semi-tensor product (STP) of matrices and the algebraic state-space representation (ASSR) of the Boolean networks, this article reveals that in addition to this explicit order, there is a certain implicit or hidden order, which is determined by the fixed points and limit cycles of their dual networks. The structure and certain properties of dual networks are investigated. Instead of a trajectory, which describes the evolution of a state, the hidden order provides a global horizon to describe the evolution of the overall network. We conjecture that the order of networks is mainly determined by the dual attractors via their corresponding hidden orders. Then these results about the Boolean networks are further extended to the k -valued case.

Incorporation of perovskite nanocrystals into lanthanide metal-organic frameworks with enhanced stability for ratiometric and visual sensing of mercury in aqueous solution.

In-situ growth of CsPbBr3 nanocrystal into Eu-BTC was realized for synthesis of dual-emission CsPbBr3@Eu-BTC by a facile solvothermal method, and a novel ratiometric fluorescence sensor based on the CsPbBr3@Eu-BTC was prepared for rapid, sensitive and visual detection of Hg2+ in aqueous solution. The transmission electron microscopy (TEM), X-ray diffraction pattern (XRD), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analysis were used to verify the successful incorporation of CsPbBr3 into the Eu-BTC. Meanwhile, the CsPbBr3@Eu-BTC nanocomposite maintained high fluorescence performance and stability in aqueous solution. After adding Hg2+, the green fluorescence of CsPbBr3 was quenched and the red fluorescence of Eu3+ remained unchanged, while the color changed from green to red obviously. The occurrence of dynamic quenching and electron transfer were verified by fluorescence lifetime, Stern-Volmer quenching constant and XPS analysis. The ratiometric fluorescence sensor shows high analytical performance for Hg2+ detection with a wide linear range of 0-1 µM and a low detection limit of 0.116 nM. In addition, it also shows high selectivity for the detection of Hg2+ and can be successfully applied to detect Hg2+ in environmental water samples. More importantly, a novel paper-based sensor based on the CsPbBr3@Eu-BTC ratiometric probe was successfully manufactured for the visual detection of Hg2+ by naked eyes. This new type of ratiometric fluorescent sensor shows great potential for applications in point-of-care diagnostics.

Ultrasensitive electrochemiluminescence determination of trace Ag ions based on the signal amplification caused by its catalytic effect on Mn(II) oxidation using graphite catheter as electrode.

In this work, an ultrasensitive electrochemiluminescence (ECL) method was established for the detection of trace amount of Ag ions (Ag+). In sulfuric acid medium, Ag(II), the electro-oxidized product of Ag(I), oxidizes manganese ions (Mn2+) to produce permanganate (MnO4-) by using a pair of graphite catheters as electrodes. While permanganate and luminol can produce strong chemiluminescence, based on the catalytic effect of Ag(II) on Mn2+ oxidation, there is a good linear relationship between the concentration of Ag+ and luminescence intensity. Under optimized conditions, the linear range of this method for Ag+ is from 0.2 to 150 nM with a detection limit of 0.06 nM. The method was applied for determination of Ag+ in various water samples with satisfactory results.