QD-Biopolymer-TSPP Assembly as Efficient BiFRET Sensor for Ratiometric and Visual Detection of Zinc Ion

In this work, we report a new type of quantum dot (QD)-based fluorescence resonance energy transfer (FRET) assembly and its utility for sensing Zn2+ in different media. The assembly on the QD scaffold is via first coating of poly­(dA) homopolymer/double-stranded DNA, followed by loading of meso-tetra­(4-sulfonatophenyl)­porphine dihydrochloride (TSPP), both of which are electrostatic, offering the advantages of cost-efficiency and simplicity. More importantly, the biopolymer coating minimizes the interfacial thickness to be ≤2 nm for QD-TSPP FRET, which results in improvements of up to 60-fold for single FRET efficiency and nearly 4-fold for total FRET efficiency of the QD-biopolymer-TSPP assemblies in comparison with silica-coating-based QD-TSPP assemblies. On the basis of Zn2+-chelation-induced spectral modulation, dual-emission QD-poly­(dA)-TSPP assemblies are developed as a ratiometric Zn2+ sensor with increased sensitivity and specificity. The sensor either in solution or on a paper substrate displays continuous color changes from yellow to bright green toward Zn2+, exhibiting excellent visualization capability. By utilizing the competitive displacement of Zn2+, the sensor is also demonstrated to have good reversibility. Furthermore, the sensor is successfully used to visualize exogenous Zn2+ in living cells. Together the QD-biopolymer-TSPP assembly provides an inexpensive, sensitive, and reliable sensing platform not only for on-site analytical applications but also for high-resolution cellular imaging

A Low-Bandgap Conjugated Copolymer Based on Porphyrin and Dithienocoronene Diimide with Strong Two-Photon Absorption

A new low-bandgap donor–acceptor (D–A) conjugated copolymer poly­(DTCDI–POR) of planar acceptor dithienocoronene diimide (DTCDI) and strong donor porphyrin (POR) has been synthesized by Sonogashira coupling polymerization. Poly­(DTCDI–POR) exhibits good thermal stability (decomposition temperature of 323 °C), strong absorption (molar extinction coefficient per repeat unit is 1.05 × 10⁵ L mol^–1 cm^–1 at 468 nm in CHCl₃ solution) in visible and near-infrared region (300–900 nm), low bandgap (1.44 eV), and strong two-photon absorption (2PA) at telecommunication wavelengths with 2PA cross sections per repeat unit as high as 7809 GM at 1520 nm

Stereochemistry of the Thermal Rearrangement through Intramolecular Metathesis of Si−Si and Fe−Fe Bonds: First Evidence for a Nonconcerted Mechanism

meso and rac isomers of (η5:η5-C5H4RMeSiSiMeRC5H4)Fe2(CO)2(μ-CO)2 (R = Ph, n-Bu) were synthesized and successfully separated for the first time. They were found to undergo the title rearrangement reaction in a nonstereospecific fashion, to give the products [RMeSi-η5-C5H4Fe(CO)2]2 as mixtures of meso and rac isomers in ratios of about 1:1. This is direct evidence to rule out the concerted free radical mechanism that is currently used to explain this reaction. A new mechanism involving activation of the Si−Si bond by a coordinatively unsaturated iron center is suggested

Porphyrin−Dithienothiophene π-Conjugated Copolymers: Synthesis and Their Applications in Field-Effect Transistors and Solar Cells

Soluble conjugated alternating porphyrin−dithienothiophene copolymerssingle-bond linked (I) and triple-bond linked (IIa and IIb)were synthesized by palladium(0)-catalyzed Stille and Sonagashira coupling reactions, respectively. The thermal, electrochemical, optical, charge transport, and photovoltaic properties of these copolymers were examined; the effect of the triple bond was studied. I exhibits onset decomposition temperature (Td) of 410 °C and glass-transition temperature (Tg) of 180 °C, higher than those of IIb (Td, 330 °C; Tg, 130 °C). The absorption spectrum of I in thin film exhibits a sharp Soret band at 450 nm and two weak Q-bands at 563−619 nm, while IIb exhibits a sharp Soret band at 491 nm and a strong Q-band at 760 nm. The emission maxima of I and IIb in solution are located at 642 and 722 nm respectively. IIb is electrochemically active in both the oxidation and reduction regions, while I shows only oxidation peak. The field-effect hole mobilities as high as 2.1 × 10−4 cm2 V−1 s−1 were obtained for these copolymers. Polymer solar cells (PSCs) were fabricated based on the blend of the polymers and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM). The power conversion efficiency (PCE) of 0.3% was achieved under AM 1.5, 100 mW/cm2 for the PSC using IIb:PCBM (1:3, w/w) as active layer. The PCE of the PSC based on IIb:PCBM (1:3, w/w) is double that based on I:PCBM (1:2, w/w), consistent with that IIb exhibits stronger Q-band absorption and higher mobility at room temperature

Molecularly Imprinted Membrane Electrospray Ionization for Direct Sample Analyses

Typically dealing with practical samples with very complex matrices, ambient ionization mass spectrometry suffers from low detection sensitivity. In this study, molecular imprinting technology was explored and integrated with the membrane electrospray ionization (MESI) method for direct sample analyses. By enriching targeted analytes on molecularly imprinted membranes (MIMs), improvement (by 10- to 50-fold) in the limit of quantitation could be achieved, compared to conventional nanoelectrospray ionization methods or other ambient ionization methods. MIMs were prepared by cross-linking a synthesized molecularly imprinted polymer layer onto a polyvinylidene difluoride (PVDF) membrane. The characteristics of MIM in recognizing target analytes were investigated and verified. Experiments showed that MIM-ESI could provide satisfactory performances for direct quantification of targeted analytes in complex samples using mass spectroscopy (MS), and the quantitative performance of this methodology was validated. With the capability of target enrichment, the uses of MIM-ESI MS in different application fields were also demonstrated, including food safety, quantification of drug concentrations in blood, pesticide residues in soil, and antibiotic residues in milk