Latest ArticlesThe massive use of polyhexamethylene guanidine (PHMG), as a typical bactericidal agent, raised environmental concerns to the public. This work comprehensively revealed the hormesis effects of PHMG occurred in waste activated sludge (WAS) on the generation of volatile fatty acids (VFAs) during anaerobic fermentation. The low level of PHMG (100 mg/g TSS) significantly promoted the VFAs generation (1283 mg COD/L, compared with 337 mg COD/L in the control) via synchronously facilitating the solubilization, hydrolysis, and acidification steps but inhibiting methanogenesis. Metagenomic analysis showed that the functional anaerobe (i.e., Bacteroides, Macellibacteroide and Parabacteroide) and corresponding genetic expressions responsible for extracellular hydrolysis (i.e., clpP), membrane transport (i.e., ffh and gspF), intracellular substrates metabolism (i.e., ald and paaF) and VFAs biosynthesis (i.e., ACACA and FASN) were enhanced in the optimal presence of PHMG. Moreover, the anaerobic species could respond and adapt to low PHMG stimuli via quorum sensing (i.e., cqsA, rpfC and rpfG), and thus maintain the high microbial metabolic activities. However, they were unable to tolerate the toxicity of excessive PHMG, resulting in the extremely low VFAs production. This work enlightened the effects of emerging pollutants on WAS fermentation at the genetic levels, and provided guidance on the WAS treatment and resource recovery.
Development of high-performance solid state luminescent carbon-based nanomaterials remains challenging. Here, strong blue-green fluorescent carbonized polymer dots (CPDs) from o-aminobenzenethiol and thiosalicylic acid (oABT-TSA-CPDs) with an absolute photoluminescence quantum yield (PLQY) of 76% in solid state without matrix were synthesized. Through adjusting the reaction temperature and time, the PL centers were proved to be carbon core state and surface state associated to carbonyl group which was the source of strong fluorescence emission in solid state. The mechanism of the unique phenomenon of enhanced emission from ethanol solution (PLQY = 7%) to powder (PLQY = 76%) was investigated by analyzing the chemical properties and structures of oABT-TSA-CPDs at different temperatures and oABT-TSA-CPDs/PVC composites, and was confirmed as fixation of PL centers.
The electrochemical CO2 reduction reaction (CO2ER) is an emerging process that involves utilizing CO2 to produce valuable chemicals and fuels by consuming excess electricity from renewable sources. Recently, Cu and Cu-based nanoparticles, as earth-abundant and economical metal sources, have been attracting significant interest. The chemical and physical properties of Cu-based nanoparticles are modified by different strategies, and CO2 can be converted into multicarbon products. Among various Cu-based nanoparticles, Cu-based metal-organic frameworks (MOFs) are gaining increasing interest in the field of catalysis because of their textural, topological, and electrocatalytic properties. In this minireview, we summarized and highlighted the main achievements in the research on Cu-based MOFs and their advantages in the CO2ER as electrocatalysts, supports, or precursors.
By introducing a naphthothiadiazole (NT) unit as the main building block, a non-doped and red emissive conjugated polymer poly(9,9-dihexylfluorene-alt-naphthothiadiazole) (PFNT) is readily obtained through a two-step synthesis. Since the NT unit has a large twist angle with its neighboring segment, the aggregation-induced quenching (AIQ) effect of PFNT can be effectively suppressed in the condensed state. As a result, the corresponding PFNT polymer dot (Pdot) exhibits a high fluorescence quantum yield of 53.2% with peak emission at 616 nm, which is one of the most efficient red Pdots known. PFNT Pdot shows good biocompatibility and can be employed for living cell fluorescent imaging with high brightness. It also can be used for specific subcellular organelle imaging through immunofluorescence labeling. Furthermore, the PFNT Pdot demonstrates much better photostability for long-time cell fluorescence imaging than commercial red dyes. The high performances of PFNT Pdot make it a promising fluorescent probe for practical bioapplications.
The domain purity, material crystallinity and distribution at the interface between the active layer and the transport layer have an important impact on the performance of organic solar cells (OSCs) and organic photodetectors (OPDs), while this focal issue has received less attention in previous studies. From this perspective, a new method to simultaneously enhance the performance of OSC and OPD is proposed, namely, using a sequential deposition method to first construct a compact stacking structure of dual-donor (D18-Cl:PTO2) eutectic in the donor layer, and then induce the ordered deposition of the acceptor (Y6). Compared with the conventional bulk heterojunction (BHJ), the active layer realized by this method not only improves the crystallinity and stacking order of the constituent material on the surface of the transport layer, but also regulates a good vertical distribution, which is conducive to improving the charge transport and extraction efficiency, reducing the leakage current, and enhancing the stability of the device. As a result, the OSC device based on the D18-Cl:PTO2/Y6 structure achieves a power conversion efficiency of up to 17.65% and good light-degradation stability, which is much better than that of BHJ-based OSC (PCE of 16.37%). For the OPD, the dark current at reverse bias is reduced by more than an order of magnitude, and the maximum responsivity is improved to 0.52 A/W through the optimization of the donor phase at the interface. Moreover, the strategy does not require additional post-processing compared to the BHJ preparation, which reduces the device construction cost and process complexity, providing an effective way for developing high-performance organic optoelectronic devices.
Conductive hydrogels have shown great prospects as wearable flexible sensors. Nevertheless, it is still a challenge to construct hydrogel-based sensor with great mechanical strength and high strain sensitivity. Herein, an ion-conducting hydrogel was fabricated by introducing gelatin-dialdehyde β-cyclodextrin (Gel-DACD) into polyvinyl alcohol-borax (PVA-borax) hydrogel network. Natural Gel-DACD network acted as mechanical deformation force through non-covalent cross-linking to endow the polyvinyl alcohol-borax/gelatin-dialdehyde β-cyclodextrin hydrogel (PGBCDH) with excellent mechanical stress (1.35 MPa), stretchability (400%), toughness (1.84 MJ/m3) and great fatigue resistance (200% strain for 100 cycles). Surprisingly, PGBCDH displayed good conductivity of 0.31 S/m after adding DACD to hydrogel network. As sensor, it showed rapid response (168 ms), high strain sensitivity (gage factor (GF) = 8.57 in the strain range of 200%-250%) and reliable sensing stability (100% strain for 200 cycles). Importantly, PGBCDH-based sensor can accurately monitor complex body movements (knee, elbow, wrist and finger joints) and large-scale subtle movements (speech, swallow, breath and facial expressions). Thus, PGBCDH shows great potential for human monitoring with high precision.
Developing redox switches that not only perform specific mechanical movements but also drive important chemical reactions is important but a great challenge. Herein, we report a redox pair of cobalt species (CoⅢ/CoⅡ) that switches through photo-dehydrogenation of alcohol and hydrogenation of azo-ligand. The cobalt species is equipped with a flexible azo-ligand containing two bulky planar substituents. A planar oxidated sate (CoⅢ species) can be photo-reduced to a saddle-like reduced state (CoⅡ) with alcohol molecules as electron donors, and in turn the CoⅢ species can be recovered with azo-ligand as oxidant under acidic surrounding. Both the redox states of the pair are isolated and characterized by single crystal X-ray diffraction. In the switching cycle, alcohol is oxidized to aldehyde by azo-ligand through proton coupled electron transfer and the cobalt complex acts as a redox catalyst. These results provide important insights into alcohol dehydrogenation catalyzed by redox complexes.
Nanopore detection is a hot issue in current research. One of the challenges is how to slow down the transport velocity of nanoparticles in nanopores. In this paper, we propose a functional group modified nanopore. That means a polyelectrolyte brush layer is grafted on the surface of the nanopore to change the surface charge properties. The existing studies generally set the charge density of the brush layer to a fixed value. On the contrary, in this paper, we consider an essential property of the brush layer: the volume charge density is adjustable with pH. Thus, the charge property of the brush layer will change with the local H+ concentration. Based on this, we established a mathematical model to study the transport of nanoparticles in polyelectrolyte brush layer modified nanopores. We found that pH can effectively adjust the charge density and even the polarity of the brush layer. A larger pH can reduce the transport velocity of nanoparticles and improve the blockade degree of ion current. The grafting density does not change the polarity of the brush charge. The larger the grafting density, the greater the charge density of the brush layer, and the blockade degree of ion current is also more obvious. The polyelectrolyte brush layer modified nanopores in this paper can effectively reduce the nanoparticle transport velocity and retain the essential ion current characteristics, such as ion current blockade and enhancement.
Schisandrin A is a natural dibenzocyclooctene lignan with potent neuroprotective activity. However, the specific mechanisms or direct target proteins have not been clarified up to now. In this study, we designed and synthesized the probes of schisandrin A with photoreactive diazirine and clickable alkyne to identify its direct target in SH-SY5Y cells by employing activity-based protein profiling (ABPP) technique. Ykt6 was prominent among the 13 proteins obtained with high confidence and we confirmed Ykt6 as the direct target of schisandrin A by CETSA, IF, SPR and knockdown assay. Functionally, schisandrin A protected the cells against the injury induced by glutamate by regulating autophagy via Ykt6. This discovery may provide a novel therapeutic option for various neuronal cell damage-mediated diseases.
The electrochemical nitrogen reduction reaction (NRR) for the ammonia production under ambient conditions is regarded as a sustainable alternative to the industrial Haber–Bosch process. However, the electrocatalytic systems that efficiently catalyze nitrogen reduction remain elusive. In the work, the nitrogen reduction activity of the transition metal decorated bismuthene TM@Bis is fully investigated by means of density functional theory calculations. Our results demonstrate that W@Bis delivers the best efficiency, wherein the potential-determining step is located at the last protonation step of *NH2 + H+ + e– → *NH3 via the distal mechanism with the limiting potential UL of 0.26 V. Furthermore, the dopants of Re and Os are also promising candidates for experimental synthesis due to its good selectivity, in despite of the slightly higher UL of NRR with the value of 0.55 V. However, the candidates of Ti, V, Nb and Mo delivered the relative lower UL of 0.35, 0.37, 0.41 and 0.43 V might be suffered from the side hydrogen evolution reaction. More interestingly, a volcano curve is established between UL and valence electrons of metal elements wherein W with 4 electrons in d band located at the summit. Such phenomenon originates from the underlying acceptance-back donation mechanism. Therefore, our work provides a fundament understanding for the material design for nitrogen reduction electrocatalysis.
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