Electrochemistry and Electrochemiluminescence of Organometal Halide Perovskite Nanocrystals in Aqueous Medium

The redox nature and electrochemiluminescence (ECL) of highly crystallized organometal halide perovskite CH₃NH₃PbBr₃ nanocrystals (NCs) in aqueous medium were investigated for the first time. CH₃NH₃PbBr₃ NCs could be electrochemically reduced to negative charge states by injecting electrons into the lowest unoccupied molecular orbitals and oxidized to positive charge states by removing electrons from the highest occupied molecular orbitals; charge transfer between NCs with positive and negative charge states could produce ECL. The redox sequence of CH₃NH₃PbBr₃ NCs played an important role in the generation of charge-transfer-mediated ECL; transient ECL could be achieved only by electrochemically reducing positive-charged NCs in an annihilation route. A large redox current was unfavorable for ECL. Charge mobility within CH₃NH₃PbBr₃ NCs had an important effect on ECL intensity in a co-reactant route, which is promising for photovoltaic and optoelectronic device applications. Importantly, the ECL spectra of CH₃NH₃PbBr₃ NCs were almost identical to their photoluminescence spectra, with a maximum emission around 535 nm and full width at half-maximum around 25 nm; this might open a way to obtaining monochromatic ECL using highly crystallized NCs as emitters, which makes them promising for use in color-selective ECL analysis

Temperature-Dependent Order-to-Order Transition of Polystyrene-<i>block</i>-poly(ethylene-<i>co</i>-butylene)-<i>block</i>-polystyrene Triblock Copolymer under Multilayered Confinement

The order-to-order transition (OOT) plays a key role in the nanotechnological applications of block copolymer (BCP) and is dramatically dependent on the spatial environment. A multilayer-confined space has been fabricated by layer-multiplying coextrusion technology to investigate the OOT mechanism of polystyrene-<i>block</i>-poly­(ethylene-<i>co</i>-butylene)-<i>block</i>-polystyrene triblock copolymer (SEBS) under multilayered confinement. The parallel oriented ordering front, whose OOT temperature is lower than that of the bulk due to higher free energy, is induced by the “substrate surface effect” in the SEBS layers of the multilayer specimens. The OOT temperature of SEBS is mainly decided by the volume fraction of ordering front. The propagation distance maximum of the “substrate surface effect” is about 220 nm. Only when the thickness of SEBS layer is less than this critical value is the whole SEBS layer fully filled with the ordering front. As a result, the OOT temperature first decreases rapidly and then tends to be a constant value with the decrease of layer thickness. This turning point of layer thickness is found to locate around 220 nm. Finally, the change of transition temperature region with the layer thickness has been explained by the fact that the bulk, thin layer samples (less than turning point) and thick layer samples (more than turning point) have different OOT mechanisms

Spectrum-Resolved Dual-Color Electrochemiluminescence Immunoassay for Simultaneous Detection of Two Targets with Nanocrystals as Tags

A spectrum-resolved dual-color electrochemiluminescence (ECL) immunoassay was designed and implemented to simultaneously detect carcinoembryonic antigen (CEA) and alpha fetoprotein (AFP) with CdTe (λ_max = 776 nm) and CdSe (λ_max = 550 nm) nanocrystals (NCs) as ECL tags. The CdTe and CdSe NCs were labeled with respective probe antibodies (Ab₂) of CEA and AFP, respectively, and then immobilized onto the working electrode surface via sandwich-type immunoreactions. Both CdTe and CdSe NCs within the NCs immunocomplexes can be electrochemically reduced and simultaneously give off monochromatic ECL emissions in the near-infrared and greenish regions, respectively, when (NH₄)₂S₂O₈ was used as a cathodic ECL coreactant. The ECL spectra of the two surface-confined NCs were well separated and had no cross energy-transfer interactions, which made the dual-color immunoassay highly selective and sensitive toward respective target analytes. With the proposed ECL biosensor, CEA and AFP were simultaneously detected and quantified with an extremely low detection limit of 1 pg/mL for CEA and 10 fg/mL for AFP, respectively. This work demonstrated the probability of performing multianalyte assays via a spectrum-resolved ECL strategy with improved sensitivity and signal-to-noise ratio as compared to NCs-based fluorescent multianalyte assays

Spectrum-Based Electrochemiluminescent Immunoassay with Ternary CdZnSe Nanocrystals as Labels

Conventional electrochemiluminescence (ECL) research has been performed by detecting the total photons (i.e., the ECL intensity). Herein, systematic spectral exploration on the ECL of dual-stabilizers-capped ternary CdZnSe nanocrystals (NCs) and its sensing application were carried out on a homemade ECL spectral acquiring system. The ternary CdZnSe NCs could be repeatedly injected with electrons via some electrochemical ways and then result in strong cathodic ECL with the coupling of ammonium persulfate. ECL spectrum of the CdZnSe NCs was almost identical to corresponding photoluminescence spectrum, indicating that the excited states of CdZnSe NCs in ECL were essentially the same as those in photoluminescence. Importantly, after being labeled to the probe antibody (Ab₂) of α-fetal protein (AFP) antigen, the ternary NCs in the Ab₂|NCs conjugates could preserve their ECL spectrum very well. A spectrum-based ECL immunoassay was consequently proposed with the CdZnSe NCs as ECL tags and AFP as target molecules. The limit of detection is 0.010 pg/mL, with a signal-to-noise (S/N) ratio of 3, indicating a sensitive ECL sensing strategy that was different from the conventional ones. This work might open a pathway to the spectrally resolved ECL analysis with even-higher S/N ratios than the fluorescent analysis

Discovery of Covalent Ligands via Noncovalent Docking by Dissecting Covalent Docking Based on a “Steric-Clashes Alleviating Receptor (SCAR)” Strategy

Covalent ligands modulating protein activities/signals have attracted unprecedented attention in recent years, but the insufficient understanding of their advantages in the early days of drug discovery has hindered their rational discovery and development. This also left us inadequate knowledge on the rational design of covalent ligands, e.g., how to balance the contribution from the covalent group and the noncovalent group, respectively. In this work, we dissected the noncovalent docking from covalent docking by creating SCARs (steric-clashes alleviating receptors). We showed that the SCAR method outperformed those specifically developed but more complicated covalent docking protocols. We furthermore provided a “proof-of-principle” example by implementing this method in the first high-throughput screening and discovery of novel covalent inhibitors of <i>S</i>-adenosylmethionine decarboxylase. This work demonstrated that noncovalent groups play a predeterminate role in the design of covalent ligands, and would be of great value in accelerating the discovery and development of covalent ligands

Randomization-Based Inference for Clinical Trials with Missing Outcome Data

Randomization-based inference is a natural way to analyze data from a clinical trial. But the presence of missing outcome data is problematic: if the data are removed, the randomization distribution is destroyed and randomization tests have no validity. In this paper we describe two approaches to imputing values for missing data that preserve the randomization distribution. We then compare these methods to population-based and parametric imputation approaches that are in standard use to compare error rates under both homogeneous and heterogeneous population models. We also describe randomization-based analogs of standard missing data mechanisms and describe a randomization-based procedure to determine if data are missing completely at random. We conclude that randomization-based methods are a reasonable approach to missing data that perform comparably to population-based methods.</p

Exploration of the Hydrogen-Bonded Energetic Material Carbohydrazide at High Pressures

We have reported the high-pressure behavior of hydrogen-bonded energetic material carbohydrazide (CON₄H₆, CHZ) via <i>in situ</i> Raman spectroscopy and angle-dispersive X-ray diffraction (ADXRD) in a diamond anvil cell with ∼15 GPa at room temperature. Significant changes in Raman spectra provide evidence for a pressure-induced structural phase transition in the range of ∼8 to 10.5 GPa. ADXRD experiments confirm this phase transition by symmetry transformation from <i>P</i>2₁/<i>n</i> to a possible space group <i>P</i>1̅, which exhibits ∼23.1% higher density at 10.1 GPa compared to phase <i>P</i>2₁/<i>n</i> at ambient pressure. Moreover, the observed transition is completely reversible when the pressure is totally released. On the basis of the decreased number of hydrogen bonds, the shortened hydrogen bond lengths, and the variations in the NH and NH₂ stretching Raman peaks in the high-pressure phase, we propose that this phase transition is caused by the rearrangement of the hydrogen-bonded networks

Comparison of Four Quantitative Techniques for Monitoring Microalgae Disruption by Low-Frequency Ultrasound and Acoustic Energy Efficiency

Ultrasound has been regarded as an environmental friendly technology to utilize microalgae biomass and control algal blooms. In this study, four quantitative techniques, including cell counting, optical density of algal suspension, pigments release, and protein release, were performed on three species of microalgae (<i>M. aeruginosa</i>, <i>C. pyrenoidosa</i>, and <i>C. reinhardtii</i>) to develop effective techniques for rapid monitoring of cell disruption and to optimize the acoustic energy efficiency. Results showed optical density of algal suspensions was not an optimal indicator to monitor cell disruption, although it is a common technique for determining cell concentration in microbial cultures. Instead, an accurate and reliable technique was to determine the release of intracellular pigments (absorbance peaks of supernatant) for indicating cell rupture. The protein released during sonication could also be a useful indicator if it is the component of interest. A fitted power functional model showed a strong relationship between cell disruption and energy consumption (<i>R</i>² > 0.87). This model could provide an effective approach to directly compare the energy efficiency of ultrasound in different systems or with varying microalgae species. This study provides valuable information for microalgae utilization and the treatment of algal blooms by ultrasound, so as to achieve energy conservation and environmental safety

Current-voltage waveforms of the plasma discharge.

<p>Current-voltage waveforms of the plasma discharge.</p

Real-time monitoring of nucleus changes of the single HepG2 cell after 15 s of the plasma treatment.

<p>The cell labeling is the same as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0101299#pone-0101299-g004" target="_blank">Figure 4</a>.</p