Membrane Electrode Assembly for Electrocatalytic CO2 Reduction: Principle and Application

Electrocatalytic CO₂ reduction reaction (CO₂RR) in membrane electrode assembly (MEA) systems is a promising technology. Gaseous CO₂ can be directly transported to the cathode catalyst layer, leading to enhanced reaction rate. Meanwhile, there is no liquid electrolyte between the cathode and the anode, which can help to improve the energy efficiency of the whole system. The remarkable progress achieved recently points out the way to realize industrially relevant performance. In this review, we focus on the principles in MEA for CO₂RR, focusing on gas diffusion electrodes and ion exchange membranes. Furthermore, anode processes beyond the oxidation of water are considered. Besides, the voltage distribution is scrutinized to identify the specific losses related to the individual components. We also summarize the progress on the generation of different reduced products together with the corresponding catalysts. Finally, the challenges and opportunities are highlighted for future research.     

Phosphine-Triggered Structural Defects in Au44 Homologues Boost Electrocatalytic CO2 Reduction

The systematic induction of structural defects at the atomic level is crucial to metal nanocluster research because it endows cluster-based catalysts with highly reactive centers and allows for a comprehensive investigation of viable reaction pathways. Herein, by substituting neutral phosphine ligands for surface anionic thiolate ligands, we establish that one or two Au₃ triangular units can be successfully introduced into the double-stranded helical kernel of Au₄₄(TBBT)₂₈, where TBBT=4-tert-butylbenzenethiolate, resulting in the formation of two atomically precise defective Au₄₄ nanoclusters. Along with the regular face-centered-cubic (fcc) nanocluster, the first series of mixed-ligand cluster homologues is identified, with a unified formula of Au₄₄(PPh₃)_n(TBBT)_28−2n (n=0–2). The Au₄₄(PPh₃)(TBBT)₂₆ nanocluster having major structural defects at the bottom of the fcc lattice demonstrates superior electrocatalytic performance in the CO₂ reduction to CO. Density functional theory calculations indicate that the active site near the defects significantly lowers the free energy for the *COOH formation, the rate-determining step in the whole catalytic process.     

Spatially Resolved Organic Whispering-Gallery-Mode Hetero-Microrings for High-Security Photonic Barcodes

Whispering-gallery-mode (WGM) microcavities featuring distinguishable sharp peaks in a broadband exhibit enormous advantages in the field of miniaturized photonic barcodes. However, such kind of barcodes developed hitherto are primarily based on microcavities wherein multiple gain medias were blended into a single matrix, thus resulting in the limited and indistinguishable coding elements. Here, a surface tension assisted heterogeneous assembly strategy is proposed to construct the spatially resolved WGM hetero-microrings with multiple spatial colors along its circular direction. Through precisely regulating the charge-transfer (CT) strength, full-color microrings covering the entire visible range were effectively acquired, which exhibit a series of sharp and recognizable peaks and allow for the effective construction of high-quality photonic barcodes. Notably, the spatially resolved WGM hetero-microrings with multiple coding elements were finally acquired through heterogeneous nucleation and growth controlled by the directional diffusion between the hetero-emulsion droplets, thus remarkably promoting the security strength and coding capacity of the barcodes. The results would be useful to fabricate new types of organic hierarchical hybrid WGM heterostructures for optical information recording and security labels.     

Direct Assembly of Metal-Phenolic Network Nanoparticles for Biomedical Applications

Coordination assembly offers a versatile means to developing advanced materials for various applications. However, current strategies for assembling metal-organic networks into nanoparticles (NPs) often face challenges such as the use of toxic organic solvents, cytotoxicity because of synthetic organic ligands, and complex synthesis procedures. Herein, we directly assemble metal-organic networks into NPs using metal ions and polyphenols (i.e., metal-phenolic networks (MPNs)) in aqueous solutions without templating or seeding agents. We demonstrate the role of buffers (e.g., phosphate buffer) in governing NP formation and the engineering of the NP physicochemical properties (e.g., tunable sizes from 50 to 270 nm) by altering the assembly conditions. A library of MPN NPs is prepared using natural polyphenols and various metal ions. Diverse functional cargos, including anticancer drugs and proteins with different molecular weights and isoelectric points, are readily loaded within the NPs for various applications (e.g., biocatalysis, therapeutic delivery) by direct mixing, without surface modification, owing to the strong affinity of polyphenols to various guest molecules. This study provides insights into the assembly mechanism of metal-organic complexes into NPs and offers a simple strategy to engineer nanosized materials with desired properties for diverse biotechnological applications.     

Supracluster Assembly of Archimedean Cages with 72 Hydrogen Bonds for the Aldol Addition Reaction

Clusters that can be experimentally precisely characterized and theoretically accurately calculated are essential to understanding the relationship between material structure and function. Here, we propose the concept of “supraclusters”, which aim to connect “supramolecules” and “suprananoparticles” as well as reveal the unique assembly behavior of “supraclusters” with nanoparticle size at the molecular level. The implementation of supraclusters is full of challenges due to the difficulty in satisfying the ordered connectivity of clusters due to their abundant and dispersed hydrogen bonding sites. By solvothermal synthesis under a high catechol (H₂CATs) content, we successfully isolated a series of triangular {Al₆M₃} cluster compounds possessing brucite-like structural features. Interestingly, eight {Al₆M₃} clusters form 72-fold strong hydrogen bonding truncatedhexahedron Archimedean {Al₆M₃}₈ supracluster cage (abbreviated as H-tcu ). Surprisingly, the solution stability of the H-tcu was further proved by electrospray ionization mass spectrometry (ESI-MS) characterization. Therefore, it is not difficult to explain the reason for assembly of H-tcu into edge-directed and vertex-directed isomers. These porous supraclusters can be obtained by scale-up synthesis and exhibit a noticeable catalysis effect towards the condensation of acetone and p-nitrobenzaldehyde. As an intermediate state of supramolecule and suprananoparticle, the supracluster assembly can enrich the cluster chemistry and bring new structural types.     

An Activatable Near-Infrared Fluorescent Probe for Precise Detection of the Pulmonary Metastatic Tumors: A Traditional Molecule Having a Stunning Turn

An accurate detection of lung metastasis is of great significance for making better treatment choices and improving cancer prognosis, but remains a big challenge in clinical practice. In this study, we propose a reinventing strategy to develop a pH-activatable near-infrared (NIR) fluorescent nanoprobe, pulmonary metastasis tracer (denoted as PMT), based on assembly of NIR dye IR780 and calcium phosphate (CaP). By delicately tuning the intermolecular interactions during the assembly process and dye doping content, as well as the synthetic condition of probe, the fluorescence of PMT could be finely adjusted via the tumor acidity-triggered disassembly. Notably, the selected PMT9 could sharply convert subtle pH variations into a distinct fluorescence signal to generate high fluorescence ON/OFF contrast, dramatically reducing the background signals. Benefiting from such preferable features, PMT9 is able to precisely identify not only the tumor sites in orthotopic lung cancer models but also the pulmonary metastases in mice with remarkable signal-to-background ratio (SBR). This study provides a unique strategy to turn shortcomings of traditional dye IR780 during in vivo imaging into advantages and further expand the application of fluorescent probe to image lung associated tumor lesions.     

Preparation and Photocatalytic Activity of TiO2 Films on Silica Glass Substrates by Assembly Technique

Nanostructured TiO₂ coating films on silica glass substrates were prepared by the assembly technique. TiO₂ colloids were synthesized employing the sol‐gel method using TiCl₄ as a precursor. The effect on the surface structures which was caused by the polyethylene glycol (PEG) added to the precursor solution and the photocatalytic activity were studied. The experimental results showed that the cobble‐like TiO₂ coating films were synthesized at 500 °C. On the surface of the samples, TiO₂ films exhibited uniform shape and a narrow size distribution. The result of proper PEG added to the precursor solution led to the decreasing of the size of TiO₂ particles and the increasing of the surface area of the samples. The photocatalytic activity of TiO₂ films with PEG was higher than that of samples without PEG.     

碳纳米管介电电泳精确及可控组装技术

碳纳米管(CNTs)具有优良的电学、热学、光学、力学性能和大的长径比,使得碳纳米管在能源存储、生物医药学、催化剂载体、水气过滤、复合材料等领域存在极大的应用价值。碳纳米管在金属电极之间的精确可控组装是实现其诸多应用的前提,介电电泳法是目前最常用且最具前景的组装方法之一。文中介绍了介电电泳法组装碳纳米管的原理,分析了介电电泳组装碳纳米管的影响因素,分别从碳纳米管的精确定位组装和数量可控组装两个方面进行了综述。     

Systematic data generation and test design for solution algorithms on the example of SALBPGen for assembly line balancing

Recently, the importance of correctly designed computational experiments for testing algorithms has been a subject of extended discussions. Whenever real-world data is lacking, generated data sets provide a substantive methodological tool for experiments. Focused research questions need to base on specialized, randomized and sufficiently large data sets, which are sampled from the population of interest. We integrate the generation of data sets into the process of scientific testing.     

Solvent- and Temperature-Dependent Assembly in Monolayer Films of a Ferrocene-Naphthyridine Hybrid on HOPG

The formation of a monolayer film of bis-naphthyridyl ferrocene on highly oriented pyrolytic graphite (HOPG) at ambient conditions is demonstrated. The films are prepared by drop casting from different solvents. The microscopic structure of the films is understood using atomic force microscopy (AFM) and scanning tunnelling microscopy (STM). The analysis reveals two different types of Phases (I and II) in the films and the relative percentage of these phases depends on the nature of the solvents used for the preparation and the thermodynamical condition. Solvents like methanol, acetonitrile and DMF exclusively select Phase-I, whereas acetone and ethanol show a mix of both phases at room temperature. The different phases are formed by different conformers of the molecule. We also show that the selectivity of one of the phases over the other is related to the difference in the energetics for the formation of these phases.