Fluorescence lifetime estimation method for incomplete decay

A new incomplete decay signal model is proposed to describe the incomplete decay effects in a time- correlated single-photon counting (TCSPC) based fluorescence lifetime imaging (FLIM) system. Based on this model, we modified a MUltiple SIgnal Classification (MUSIC) algorithm to eliminate the incomplete decay effects. Monte Carlo simulations were carried out to demonstrate the performances of the proposed approach. Simulations show that the proposed method is insensitive to the laser pulse rate and has a larger lifetime dynamic range compared with previously reported approaches. As far as we know, this new method is the first non-fitting method that can resolve incomplete decay effects for multi-exponential decays

Rational catalyst design for N2 reduction under ambient conditions: Strategies towards enhanced conversion efficiency

Ammonia (NH3), one of the basic chemicals in most fertilizers and a promising carbon-free energy storage carrier, is typically synthesized via the Haber–Bosch process with high energy consumption and massive emission of greenhouse gases. The photo/electrocatalytic nitrogen reduction reaction (NRR) under ambient conditions has attracted increasing interests recently, providing alternative routes to realize green NH3 synthesis. Despite rapid advances achieved in this most attractive research field, the unsatisfactory conversion efficiency including a low NH3 yield rate, and limited Faradaic efficiency or apparent quantum efficiency still remains as a great challenge. The NRR performance is intrinsically related to the electronic and surface structure of catalysts. Rational design and preparation of advanced catalysts are indispensable to improve the performance (e.g., activity and selectivity) of NRR. In this Review, various strategies for the development of desirable catalysts are comprehensively summarized, mainly containing the defect engineering, structural manipulation, crystallographic tailoring, and interface regulation. State-of-the-art heterogeneous NRR catalysts, prevailing theories and underlying catalytic mechanisms, together with current issues, critical challenges, and perspectives are discussed. It is highly expected that this Review will promote the understanding of recent advances in this area and stimulate greater interests for designing promising NRR catalysts in future

Estimation of fluorescence lifetimes via rotational invariance techniques

Estimation of signal parameters via rotational invariance techniques is a classical algorithm widely used in array signal processing for direction-of-arrival estimation of emitters. Inspired by this method, a new signal model and a new fluorescence lifetime estimation via rotational invariance techniques (FLERIT) were developed for multi-exponential fluorescence lifetime imaging (FLIM) experiments. The FLERIT only requires a few time bins of a histogram generated by a time-correlated single photon counting FLIM system, greatly reducing the data throughput from the imager to the signal processing units. As a non-iterative method, the FLERIT does not require initial conditions, prior information nor model selection that are usually required by widely used traditional fitting methods, including nonlinear least square methods or maximum likelihood methods. Moreover, its simplicity means it is suitable for implementations in embedded systems for real-time applications. FLERIT was tested on synthesized and experimental fluorescent cell data showing the potentials to be widely applied in FLIM data analysis

Two−dimensional nanomaterials confined single atoms: New opportunities for environmental remediation

Two−dimensional (2D) supports confined single−atom catalysts (2D SACs) with unique geometric and electronic structures have been attractive candidates in different catalytic applications, such as energy conversion and storage, value−added chemical synthesis and environmental remediation. However, their environmental applications lack of a comprehensive summary and in−depth discussion. In this review, recent progresses in synthesis routes and advanced characterization techniques for 2D SACs are introduced, and a comprehensive discussion on their applications in environmental remediation is presented. Generally, 2D SACs can be effective in catalytic elimination of aqueous and gaseous pollutants via radical or non−radical routes and transformation of toxic pollutants into less poisonous species or highly value−added products, opening a new horizon for the contaminant treatment. In addition, in−depth reaction mechanisms and potential pathways are systematically discussed, and the relationship between the structure−performance is highlighted. Finally, several critical challenges within this field are presented, and possible directions for further explorations of 2D SACs in environmental remediation are suggested. Although the research of 2D SACs in the environmental application is still in its infancy, this review will provide a timely summary on the emerging field, and would stimulate tremendous interest for designing more attractive 2D SACs and promoting their wide applications

N evolution and physiochemical structure changes in chars during co-pyrolysis: Effects of abundance of glucose in fiberboard

© 2020 by the authors. The simple incineration of wood-based panels (WBPs) waste generates a significant amount of NOx, which has led to urgency in developing a new method for treating the N-containing biomass residues. This work aims to examine the N evolution and physiochemical structural changes during the co-pyrolysis of fiberboard and glucose, where the percentage of glucose in the feedstock was varied from 0% to 70%. It was found that N retention in chars was monotonically increased with increasing use of glucose, achieving ~60% N fixation when the glucose accounted for 70% in the mixture. Pyrrole-N (N-5) and Pyridine-N (N-6) were preferentially formed at high ratios of glucose to fiberboard. While the relevant importance of volatile–char interactions to N retention and transformation could be observed, the volatile–volatile reactions from the two feedstocks played a vital role in the increase in abundance of glucose. With the introduction of glucose, the porous structure and porosity in chars from the co-pyrolysis were dramatically altered, whereas the devolatilization of glucose tended to generate larger pores than the fiberboard. The insignificant changes in carbon structure of all chars revealed by Raman spectroscopy would practically allow us to apply the monosaccharides to the WBPs for regulating N evolution without concerns about its side effects for char carbon structures

Deformation and strength characteristics of Laves phases in titanium alloys

The superior reinforcement nature of Laves phases make them suitable for high-strength applications. Therefore, investigations on the deformation and strength characteristics of Laves phases are useful in development of an improved Laves phase-reinforced alloy. In this work, the Vickers micro-indentation method is used to evaluate and compare the deformation and strength characteristics of a hexagonal close-packed Laves phase (C14-type) in Ti-35Zr-5Fe-6Mn (wt%) and a face-centered cubic Laves phase (C15-type) in Ti-33Zr-7Fe-4Cr (wt%), considering the same volume fraction of Laves phase (~7.0%) in these alloys. Moreover, the effects of higher volume fraction of Laves phase (19.4%) on indentation-based deformation features are evaluated in Ti-35Zr-5Fe-8Mn (wt%). Remarkably, dislocation activity and plastic deformation features are evident in the C15-type Laves phase, whereas the C14-type Laves phase strongly blocks dislocation motion. Therefore, the C15-type Laves phase improves plastic deformability, whereas the C14-type Laves phase improves strength characteristics of Laves phase-reinforced alloys

MIL-53(Fe) derived magnetic CuFe2O4/Fe2O3 composite for catalytic oxidation of sulfamethoxazole via peroxymonsulfate activation

Design of metal–organic framework (MOF) derived metal oxides is an effective approach for environmental remediation. The current study describes the fabrication of MIL-53-derived perforated CuFe2O4/Fe2O3 using a facile, one-step, post-thermal solid-state approach by varying Cu/Fe ratios. Herein, the release of CO2 and H2O during the thermal treatment facilitates the incorporation of Cu2+ onto the Fe2O3 structure, forming a perforated hollow CuFe2O4/Fe2O3 composite via an in-situ ion-exchange mechanism. The optimised catalyst CF-0.5 displays a high degradation efficiency for the removal of sulfamethoxazole (SMX) by heterogeneous activation of peroxymonsulfate (PMS), ascribing to the better textural, morphological, and elemental properties of the novel catalyst. Important reaction parameters such as pH, catalyst loading, PMS dosage, pollutant kind and concentration, and reaction temperature are further optimised to develop a cost-effective catalytic system. The magnetically recoverable catalyst outlines a high stability rate, and only a 9 % efficiency loss is observed even after the fourth cycle. Reactive oxygen species (ROS) are identified by electron paramagnetic resonance spectroscopy (EPR) and their roles are determined by performing quenching experiments. In the end, a detailed study of the mineralisation ability and reaction intermediates is performed and possible pathways for the degradation mechanism are proposed. This study not only introduces a facile approach for the fabrication of MOF-driven nanomaterials but provides insights into the removal of emerging contaminants such as SMX