A bis(pyridyl)amine‐bipyridine‐iron(II) framework (Fe(BPAbipy)) of complexes 1–3 is reported to shed light on the multistep nature of CO2 reduction. Herein, photocatalytic conversion of CO2 to CO ...even at low CO2 concentration (1 %), together with detailed mechanistic study and DFT calculations, reveal that 1 first undergoes two sequential one‐electron transfer affording an intermediate with electron density on both Fe and ligand for CO2 binding over proton. The following 2 H+‐assisted Fe‐CO formation is rate‐determining for selective CO2‐to‐CO reduction. A pendant, proton‐shuttling α‐OH group (2) initiates PCET for predominant H2 evolution, while an α‐OMe group (3) cancels the selectivity control for either CO or H2. The near‐unity selectivity of 1 and 2 enables self‐sorting syngas production at flexible CO/H2 ratios. The unprecedented results from one kind of molecular catalyst skeleton encourage insight into the beauty of advanced multi‐electron and multi‐proton transfer processes for robust CO2RR by photocatalysis.
A polypyridine Fe‐based skeleton is reported for selective CO2‐to‐CO photoreduction even under 1 % CO2. Mechanistic insights reveal two sequential one‐electron transfer affording an intermediate with delocalized electron density on both Fe and ligand for CO2 addition. Proton‐assisted CO formation is crucial for CO2 reduction. A pendant, proton‐shuttling α‐OH group switches the transformation to H2 exclusively, which enables self‐sorting syngas formation at flexible CO/H2 ratios.
Multiband terahertz (THz) detectors have attractive prospects in the areas of THz sensing and imaging. This paper presents a monolithic resonant CMOS fully integrated triple-band THz thermal detector ...that is composed of a compact loop antenna and an optimized proportional to absolute temperature (PTAT) sensor, leading to an uncooled, compact, low-cost, easy-integration, and mass-production multiband detector. The principles of operation, theoretical calculation, and experimental validation are demonstrated in detail. Calculated responsivities are 34.9 V/W, 51.6 V/W, and 47.6 V/W at the operation frequencies of 0.91 THz, 2.58 THz, and 4.3 THz, respectively, for the natural atmospheric windows. Relatively better experimental results are obtained at 0.91 THz and 2.58 THz due to the scarcity of THz sources, showing maximum responsivities of 29.2 V/W and 46.5 V/W with minimum NEPs of 1.57 µW/Hz
0.5
and 1.26 µW/Hz
0.5
, respectively. The presented triple-band thermal detector has the natural scalability to focal plane arrays, providing great potential for multiband THz sensing and imaging systems.
Aiming at the construction of novel platform for efficient light harvesting, the precise synthesis of a new family of AIEgen‐branched rotaxane dendrimers was successful realized from an ...AIEgen‐functionalized 2rotaxane through a controllable divergent approach. In the resultant AIE macromolecules, up to twenty‐one AIEgens located at the tails of each branches, thus making them the first successful example of AIEgen‐branched dendrimers. Attributed to the solvent‐induced switching feature of the rotaxane branches, the integrated rotaxane dendrimers displayed interesting dynamic feature upon the aggregation‐induced emission (AIE) process. Moreover, novel artificial light‐harvesting systems were further constructed based on these AIEgen‐branched rotaxane dendrimers, which revealed impressive generation‐dependent photocatalytic performances for both photooxidation reaction and aerobic cross‐dehydrogenative coupling (CDC) reaction.
A novel artificial light‐harvesting system based on AIEgen‐branched rotaxane dendrimers has been successfully constructed which displayed impressive generation‐dependent photocatalytic performances for both photooxidation reaction and aerobic cross‐dehydrogenative coupling reaction.
A new covert luminescent anticounterfeiting (AC) technology was developed by employing combinatorial chemistry and concentration-dependent stimulus-responsive luminescent patterns. Oxygen-sensitive ...materials are carefully tailed to be inkjet printable and to form luminescent color inks. The inks are placed in the tanks of a jet printer. The printed luminescent patterns exhibited multilevel and highly secured AC features. Unlike conventional luminescent AC technology that solely relies on luminescent molecules/nanoparticles, the new technique utilizes the following features to fight counterfeiting: (1) the combination of luminescent oxygen-sensitive probes (OSPs) and the oxygen-permeable matrix (OPM), (2) the unique nonlinear oxygen-responsive behavior, (3) the local oxygen concentration, and (4) a luminescence lifetime reading device. The virtually unlimited number of codes is mainly due to the following features: (a) an almost endless number of combinations of OSPs and OPMs and (b) the nonlinearity of the Stern–Volmer plots that describe quenching of luminescence by oxygen. This combinatorial chemistry strategy makes it very difficult for counterfeiters to find the right composition even when the chemical composition of the luminescent molecules/nanoparticles was known. Information encrypted via this new methodology exhibits extremely high security, as counterfeiters need to identify all (not part of them) the following security measures: (1) the right combination of OSPs and OPMs, (2) the right chemical stimulus (here oxygen), (3) the proper oxygen concentration, and (4) the correct luminescence lifetime values.
Metal-organic frameworks (MOFs) are porous crystalline materials constructed from metal ions or clusters and multidentate organic ligands. Recently, the use of MOFs or MOF composites as catalysts for ...synergistic catalysis and tandem reactions has attracted increasing attention due to their tunable open metal centres, functional organic linkers, and active guest species in their pores. In this review, the applications of MOFs with multiple active sites in synergistic organic catalysis, photocatalysis and tandem reactions are discussed. These multifunctional MOFs can be categorized by the type of active centre as follows: (i) open metal centres and functional organic linkers in the MOF structure, (ii) active guest sites in the pores and active sites in the MOF structure, and (iii) bimetallic nanoparticles (NPs) on MOF supports. The types of synergistic catalysis and tandem reactions promoted by multifunctional MOFs and their proposed mechanisms are presented in detail. Here, catalytic MOFs with a single type of active site and MOFs that only serve as supports to enhance substrate adsorption are not discussed.
Various active sites incorporated into metal-organic frameworks (MOFs) are suitable for synergistic catalysis and tandem reactions.
We review the current state of optical methods for sensing oxygen. These have become powerful alternatives to electrochemical detection and in the process of replacing the Clark electrode in many ...fields. The article (with 694 references) is divided into main sections on direct spectroscopic sensing of oxygen, on absorptiometric and luminescent probes, on polymeric matrices and supports, on additives and related materials, on spectroscopic schemes for read-out and imaging, and on sensing formats (such as waveguide sensing, sensor arrays, multiple sensors and nanosensors). We finally discuss future trends and applications and summarize the properties of the most often used indicator probes and polymers. The ESI† (with 385 references) gives a selection of specific applications of such sensors in medicine, biology, marine and geosciences, intracellular sensing, aerodynamics, industry and biotechnology, among others.
The construction of circularly polarized luminescence (CPL) switches with multiple switchable emission states and high dissymmetry factors (glum) has attracted increasing attention due to their broad ...applications in diverse fields such as the development of smart devices and sensors. Herein, a new family of AIE‐active chiral 3rotaxanes were designed and synthesized, from which a novel CPL switching system was successfully constructed. The switching process was realized through the controlled motions of the chiral pillar5arene macrocycles along the axle through the addition or removal of the acetate anions, which not only modulated the chirality information transfer but also tuned the aggregations of the integrated 3rotaxanes, thus resulting in reversible transformations between two emission states with both high photoluminescence quantum yields (PLQYs) and high dissymmetry factors (glum) values.
The marriage of a switchable rotaxane and an AIEgen gave rise to the successful construction of a novel chiral 3rotaxane‐based CPL switching system with large glum values, remarkable difference in the glum values, and excellent cycling ability.
Extensive efforts have been devoted to synthesizing photothermal agents (PTAs) that are active in the first near-infrared (NIR) region (650–950 nm). However, PTAs for photothermal therapy in the ...second NIR window (1000–1350 nm) are still rare. Here, it is shown that two-dimensional ultrathin polypyrrole (PPy) nanosheets prepared via a novel space-confined synthesis method could exhibit unique broadband absorption with a large extinction coefficient of 27.8 L g–1 cm–1 at 1064 nm and can be used as an efficient PTA in the second NIR window. This unique optical property is attributed to the formation of bipolaron bands in highly doped PPy nanosheets. The measured prominent photothermal conversion efficiency could achieve 64.6%, surpassing previous PTAs that are active in the second NIR window. Both in vitro and in vivo studies reveal that these ultrathin PPy nanosheets possess good biocompatibility and notable tumor ablation ability in the second NIR window. Our study highlights the potential of ultrathin two-dimensional polymers with unique optical properties in biomedical applications.
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