Sequential and Selective Detection of Two Molecules with a Single Solid-Contact Chronopotentiometric Ion-Selective Electrode

A polymeric membrane ion-selective electrode (ISE) is typically designed for the determination of one specific ion using a conventional method. In this work, we demonstrate a simple, versatile, and sensitive platform for simultaneous detection of two molecules with a single ISE. Under a series of periodic galvanostatic polarization, a solid-contact ISE without ion exchanger properties under zero-current conditions has been successfully used for simultaneous detection of two opposite charged ions with high sensitivity, good selectivity, and fast reversibility. By integration of biorecognition elements with the potentiometric measurement, highly sensitive and selective detection of a broad range of different molecular targets can be predicted. As a proof of concept, a potentiometric genosensor based on magnetic beads-enzyme sandwich assay has been designed for sensitive and selective detection of pathogenic bacteria Escherichia coli O157:H7 and Staphylococcus aureus. Under optimal conditions, two bacteria nucleic acid sequences can be detected simultaneously with high sensitivity and good selectivity by using a single solid-contact potentiometric ISE. The detection limits of Escherichia coli O157:H7 DNA and Staphylococcus aureus DNA are 120 and 54 fM (3σ), respectively. Because of its simplicity, this potentiometric technique based on ISE can be an attractive tool or detector to perform two analyte measurements

Controlled Self-Assembly of Organic Microcrystals for Laser Applications

The small organic molecule <i>p</i>-distyrylbenzene (DSB) has been controllably prepared into one-dimensional microwires (1D-MWs) and 2D rhombic microdisks (2D-RMDs) by modulating the growth kinetics in the process of morphology growth. These as-prepared organic microcrystals, 1D-MWs and 2D-RMDs, exhibit a shape-dependent microcavity effect in that the single 1D-MW can act as a Fabry-Pérot (FP) mode lasing resonator while the individual 2D-RMD functions as the whispering-gallery-mode (WGM) microcavity. Moreover, as compared with the 1D FP resonators, there exists a higher quality factor (<i>Q</i>) in the WGM lasing resonator under the identical optical path length. Significantly, the lasing threshold, <i>E</i>_th = 1.02 μJ/cm², of 2D-RMDs is much lower than <i>E</i>_th = 2.57 μJ/cm² of 1D-MWs. Our demonstration can give the direction for the development of the organic solid-state microlasers

An Integrated Amplification-Free Digital CRISPR/Cas-Assisted Assay for Single Molecule Detection of RNA

Conventional nucleic acid detection technologies usually rely on amplification to improve sensitivity, which has drawbacks, such as amplification bias, complicated operation, high requirements for complex instruments, and aerosol pollution. To address these concerns, we developed an integrated assay for the enrichment and single molecule digital detection of nucleic acid based on a CRISPR/Cas13a and microwell array. In our design, magnetic beads capture and concentrate the target from a large volume of sample, which is 100 times larger than reported earlier. The target-induced CRISPR/Cas13a cutting reaction was then dispersed and limited to a million individual femtoliter-sized microwells, thereby enhancing the local signal intensity to achieve single-molecule detection. The limit of this assay for amplification-free detection of SARS-CoV-2 is 2 aM. The implementation of this study will establish a “sample-in-answer-out” single-RNA detection technology without amplification and improve the sensitivity and specificity while shortening the detection time. This research has broad prospects in clinical application

Tunable Morphology of the Self-Assembled Organic Microcrystals for the Efficient Laser Optical Resonator by Molecular Modulation

Organic single-crystalline micro/nanostructures can effectively generate and carry photons due to their smooth morphologies, high photoluminescence quantum efficiency, and minimized defects density and therefore are potentially ideal building blocks for the optical circuits in the next generation of miniaturized optoelectronics. However, the tailor-made organic molecules can be generally obtained by organic synthesis, ensuring that the organic molecules aggregate in a specific form and generate micro/nanostructures with desirable morphology and therefore act as the efficient laser optical resonator remains a great challenge. Here, the molecular modulation of the morphology on the laser optical resonator properties has been investigated through the preparation of the elongated hexagonal microplates (PHMs) and the rectangular microplates (ORMs), respectively, from two model isomeric organic molecules of 1,4-bis­(4-methylstyryl)­benzene (<i>p</i>-MSB) and 1,4-bis­(2-methylstyryl)­benzene (<i>o</i>-MSB). Significantly, fluorescence resonance phenomenon was only observed in the individual ORM other than the PHM. It indicates that the rectangular resonators possess better light-confinement property over the elongated hexagonal resonators. More importantly, optically pumped lasing action was observed in the <i>o</i>-MSB rectangular morphology microplates resonator with a high <i>Q</i> ≈ 1500 above a threshold of ∼540 nJ/cm². The excellent optical properties of these microstructures are associated with the morphology, which can be precisely modulated by the organic molecular structure. These self-assembled organic microplates with different morphologies can contribute to the distinct functionality of photonics elements in the integrated optical circuits at micro/nanoscale

Diketopyrrolopyrrole–Thiophene–Benzothiadiazole Random Copolymers: An Effective Strategy To Adjust Thin-Film Crystallinity for Transistor and Photovoltaic Properties

Three new low bandgap conjugated random copolymers, containing two acceptors diketopyrrolopyrrole (DPP) and benzothiadiazole (BTD) linked by thiophene donors, were designed and synthesized using Pd-catalyzed Stille-coupling methods. The ratio between DPP and BTD was varied from <i>N</i> = 3:7 to 1:1 to 7:3 in the polymer backbones. Thin-film device measurements indicate that these polymers exhibit different trends in field-effect mobilities and photovoltaic properties owing to adjustable nanoscale film morphologies as well as solid-state molecular packing. The hole mobilities reach 0.05, 0.17, and 0.40 cm² V^–1 s^–1 for <i>N</i> = 3:7, 1:1, and 7:3 copolymers while bulk heterojuction solar cells fabricated by using <i>N</i> = 3:7, 1:1, and 7:3 copolymers as donor and PC₆₀BM as acceptor show power conversion efficiency of 2.4%, 1.3%, and 0.5%. This work sets up a good example of effectively tuning the crystallinity of thin-film device through easily varying the composition ratios

ESR spectra obtained at ambient temperature from the irradiation of LBDE solutions.

<p>Note: (1) The initial concentrations were 20 μg L^-1 for LBDEs, 0.02 mol L^-1 for TEMP, and 10 mM for sodium azide; (2) Irradiation time was 12 min; (3) Spectrum a and b for BDE-47; spectrum c and d for BDE-28.</p

Effects of NaN₃ (10 mM) and isopropyl alcohol (100 mM) photolytic kinetics of BDE-47 and BDE-28 in ultrapure water under 300 W mercury lamp irradiation (λ> 290 nm).

<p>Effects of NaN₃ (10 mM) and isopropyl alcohol (100 mM) photolytic kinetics of BDE-47 and BDE-28 in ultrapure water under 300 W mercury lamp irradiation (λ> 290 nm).</p

Epitaxial Self-assembly of Binary Molecular Components into Branched Nanowire Heterostructures for Photonic Applications

We report a sequential epitaxial growth to prepare organic branched nanowire heterostructures (BNwHs) consisting of a microribbon trunk of 1,4-dimethoxy-2,5-di­[4′-(cyano)­styryl]­benzene (COPV) with multiple nanowire branches of 2,4,5-triphenylimidazole (TPI) in a one-pot solution synthesis. The synthesis involves a seeded-growth process, where COPV microribbons are grown first as a trunk followed by a seeded-growth of TPI nanowire branches at the pregrown trunk surfaces. Selected area electron diffraction characterizations reveal that multiple hydrogen-bonding interactions between TPI and COPV components play an essential role in the epitaxial growth as a result of the structural matching between COPV and TPI crystals. A multichannel optical router was successfully realized on the basis of the passive waveguides of COPV green photoluminescence (PL) along TPI nanowire branches in a single organic BNwH

Effect of D₂O on the photolytic rate of BDE-47 and BDE-28 in aqueous solutions under 300 W mercury lamp irradiation (λ> 290 nm).

<p>Effect of D₂O on the photolytic rate of BDE-47 and BDE-28 in aqueous solutions under 300 W mercury lamp irradiation (λ> 290 nm).</p

The estimated half-lives and rate constants for LBDEs under 300 W xenon lamp irradiation (λ> 290 nm) in water.

<p>The estimated half-lives and rate constants for LBDEs under 300 W xenon lamp irradiation (λ> 290 nm) in water.</p