Latest ArticlesSynthesis and functionalization of novel macrocyclic host molecules are important topics in supramolecular chemistry. In this work, the first amphiphilic [2]biphenyl-extended pillar[6]arene (AM-[2]BP-ExP6) was designed and synthesized with poly(ethylene glycol) chains as the hydrophilic tails and a rigid cavity as the hydrophobic core. Due to its amphiphilic nature, AM-[2]BP-ExP6 could self-assemble to stable fibers in water. What's more, AM-[2]BP-ExP6 could associate with quaternary ammonium modified tetraphenylethylene guest (QTPE) to form a 2:1 host-guest complex, accompanied by significant enhanced fluorescence. Interestingly, different like AM-[2]BP-ExP6, AM-[2]BP-ExP6⊃QTPE host-guest complex self-assembled into fluorescent particles with diameter about 310 nm, the obtained fluorescent particles can be further employed in living cell imaging.
Due to the high local concentration of substrates in confined space, porous solid Brønsted acids have been extensively explored for efficient acid-catalyzed reaction. However, the porous structures with strong Brønsted acids lack long-term stability due to chemical hydrolysis. Moreover, the products inhibition effect in confined rigid cavities severely obstructs subsequent catalysis. Here, tubular Brønsted acid catalyst with unique recognition of protons was presented by self-assembly of pH-responsive aromatic amphiphiles. The responsive assembly could mechanically transfer hydrogen ions from low-concentration acidic solution into tubular defined pores, thereby producing effective catalytic activity for Mannich reactions in mildly acidic solution. Notably, the tubular catalyst unfolded into flat sheets upon addition of triethylamine for efficient release of products, which could be recovered by subsequent acidification and the catalytic activity still remained. Therefore, the porous Brønsted acid with reversible assembly provides a new strategy for mass synthesis through increasing conversion times.
In this work, we have designed and synthesized a cyano-substituted p-phenylenevinylene derivative (PPTA), which can self-assemble into positively charged nanoparticles in an aqueous solution with a deep green fluorescence. An anionic polyelectrolyte material guar gum modified by carboxylic acid (GP5A) was chosen to build an artificial light-harvesting system (LHS) through self-assembly with PPTA, in which two acceptors Eosin Y (EY) and Nile red (NiR) were loaded into the PPTA-GP5A assemblies through electrostatic interaction and Van der Waals force. By adjusting the molar ratio of PPTA-GP5A/EY at 1:0.004, the one-step artificial LHS can exhibit high energy transfer efficiency (38.9%) and antenna effect (AE) (4.6). Subsequently, with the addition of NiR, the and AE of the two-step sequential artificial LHS were calculated to be 71.9% and 13.5, respectively. Moreover, the two-step artificial LHS constructed by the polyelectrolyte material GP5A can be used as a nanoreactor to photocatalyst alkylation of C-H bonds of phenyl vinyl sulfone (PVS) and tetrahydrofuran (THF) in water with a yield of 42%. Therefore, we have constructed an artificial LHS with two-step energy transfer based on polyelectrolytes through the electrostatic interaction to improve energy transfer efficiency, which can also be used as a nanoreactor for photocatalysis.
Photoresponsive supramolecular systems have merited extensive attention for their applications in materials science and life science. Here, we synthesized a water-soluble stiff-stilbene molecular photoswitch, exhibiting outstanding photoisomerization reaction between its (E)- and (Z)-configurations upon irradiation at distinct light. The photoswitch can assemble with cucurbit[7]uril (CB[7]) to form a superior fluorescent supramolecular complex (compared to the only guest) with excellent water solubility, which manifested dramatic photoluminescence enhancement caused by restriction of intramolecular rotation and remained good photochromic characteristics. Furthermore, introduction of CB[7] influence photoreaction quantum yield (Φ) of the stiff-stilbene, leading to reduction of ΦE→Z and increase of ΦZ→E of the stiff-stilbene. Importantly, the photoadjustable supramolecular assembly can act as a fluorescence switch, and the phototunable guest further selectively modulate G-quadruplex structure of Tel22 upon light irradiation or with addition of CB[7]. The study provides a new simple way for accurately regulating photochromic properties of molecular switches and developing smart materials with potential applications in controlled modulation of G-quadruplex, targeted biological imaging and so on.
Hydrazine hydrate (DH) is an important fine chemical intermediate and as fuel for rockets, however, it also has serious toxic for humans and environment. Developing novel materials and methods for sensitive detection of DH in water and air is an important task. In order to effectively detect DH, a novel conductive supramolecular polymer metallogel (PQ-Ag) has been constructed by the coordination of bis-5-hydroxyquinoline functionalized pillar[5]arene (PQ5) with Ag+. The metallogel PQ-Ag could realize the multi-channel sensitive detection of DH through naked-eye, fluorescence, and electrochemical methods. The lowest limit of detection (LOD) is 0.1 mg/m3 in air and 2.68 × 10−8 mol/L in water, which is lower than the standard of the US Environmental Protection Agency (EPA) for DH of maximum allowable concentration in drinking water. More importantly, an electronic device for DH detection based on the metallogel PQ-Ag was designed and prepared, which can realize conveniently and efficiently multi-channel detection and alert of DH through sound and light alarms not only in water but also in air.
Shortcut nitrification-denitrification (SCND) is widely concerned because of its low energy consumption and high nitrogen removal efficiency. However, the current difficulty lies in the stable maintenance of SCND performance, which leads to the challenge of large-scale application of this new denitrification technology. In this study, the nitrogen removal pathway from complete nitrification-denitrification (CND) to SCND was rapidly realized under high free ammonia (FA), high pH and low dissolved oxygen (DO) conditions. The variations of specific oxygen uptake rate (SOUR) of activated sludge in both processes were investigated by an online SOUR monitoring device. Different curves of SOUR from CND to SCND process were observed, and the ammonia peak obtained based on SOUR monitoring could be used to control aeration time accurately in SCND process. Accordingly, the SOUR ratio of ammonia oxidizing bacteria (AOB) to nitrite oxidizing bacteria (NOB) (SOURAOB/SOURNOB) was increased from 1.40 to 2.93. 16S rRNA Miseq high throughput sequencing revealed the dynamics of AOB and NOB, and the ratio of relative abundance (AOB/NOB) was increased from 1.03 to 3.12. Besides, SOURAOB/SOURNOB displayed significant correlations to ammonia removal rate (P < 0.05), ammonia oxidation rate / nitrite oxidation rate (P < 0.05), nitrite accumulation rate (P < 0.05) and the relative abundance of AOB/NOB (P < 0.05). Thus, a strategy for evaluation the SCND process stability based on online SOUR monitoring is proposed, which provides a theoretical basis for optimizing the SCND performance.
Membrane filtration is one of the effective approaches to harvest microalgae for industrial biofuel production. However, during the filtration process, microalgae cells and extracellular organic matter (EOM) will deposit on the membrane surface leading to reversible membrane fouling that can be removed by physical methods. When hydrophobic EOM is adsorbed on the membrane surface or inside pores, it will build up a gel layer, causing irreversible membrane fouling. Irreversible fouling can only be removed using chemical methods that will decrease membrane lifespan and increase operational costs. Here, we introduce a versatile superhydrophilic membrane with photo-Fenton self-cleaning property, which can prevent the reversible fouling and remove the irreversible fouling. Tannic acid (TA) and 3-aminopropyltriethoxysilane (APTES) were co-deposited on the polyvinylidene fluoride (PVDF) membrane via Schiff base and Michael addition reactions, and β-FeOOH nanorods were inlaid on the membrane surface by in situ mineralization. The water contact angle of the modified membrane is reduced from 120° to 0° Under 60 min visible light, the hydroxyl radical (·OH) generated by the photo-Fenton reaction degraded the irreversible fouling that blocked membrane pores. The irreversible fouling rates of modified membrane was reduced from 39.57% to 3.26%, compared with the original membrane. Microalgae harvesting results illustrated that the membrane has a high flux recovery rate (FRR) of 98.2%, showed excellent passive antifouling and active antifouling performance. We believe this work will spark a novel platform for optimizing energy-efficient microalgae harvesting separation membrane modules. In addition, this method of anti-fouling filtration for microorganisms can be extended to the industrial production of various bioenergy sources and will have very promising practical applications.
The combination of cyclopentadiene, β-diketonate and tripyrazoylborate ligands with dysprosium ion afforded five mononuclear compounds: [(Cp)2Dy(Tp*)] (1Dy), [(Cp)Dy(Tp*)Cl(THF)] (2Dy), [(Cp)Dy(Tp)Cl(THF)] (3Dy), [(DBM)Dy(Tp)Cl(THF)] (4Dy), [{(Tp)Dy(DBM)2(H2O)}·THF] (5Dy) (Cp = cyclopentadiene; Tp* = hydrotris(3,5-dimethyl-1-pyrazolyl)borate; Tp = hydrotris(1-pyrazolyl)borate; DBM = dibenzoylmethanoate). Magnetic study revealed that 1Dy and 3Dy exhibited typical butterfly-type hysteresis. AC susceptibility study combined with ab initio calculations indicated that the magnetic relaxation behaviors of 1Dy–4Dy were governed by the Orbach and Raman processes under applied DC field. Moreover, 3Dy showed two-step magnetic relaxation, which was attributed to the static disordering of the coordinated THF molecule. Magnetic anisotropy analysis indicated that it was the relative strength of the interactions between DyIII and surrounding ligands that determined the orientation of the magnetic easy axis.
Current clinical treatments cannot effectively delay the progression of osteoarthritis (OA). Consequently, joint replacement surgery is required for late-stage OA when patients cannot tolerate pain and joint dysfunction. Therefore, the prevention of OA progression in the early and middle stages is an urgent clinical problem. In a previous study, we demonstrated that NDRG3-mediated hypoxic response might be closely related to the development and progression of OA. In this study, an injectable thermosensitive hydrogel was established by cross-linking Pluronic F-127 and hyaluronic acid (HA) for the sustained release of hypoxia-induced exosomes (HExos) derived from adipose-derived mesenchymal stem cells. We demonstrated that for OA at the early and middle stages, the HExos-loaded HP hydrogel could maintain the chondrocyte phenotype by enhancing chondrocyte autophagy, reducing chondrocyte apoptosis, and promoting chondrocyte activity and proliferation through the NDRG3-mediated hypoxic response. This novel composite hydrogel, which could activate the NDRG3-mediated hypoxic response, may provide new ideas and a theoretical basis for the treatment of early- and mid-stage OA.
Rosmarinic acid (RA) is promising as a natural and nontoxic food additive. However, many analysis methods for RA generally depend on large instruments and single signals for quantitative detection. A new up-conversion fluorescence, colorimetric and photothermal multi-modal sensing strategy is developed for the quantification of RA. β-cyclodextrin (CD) modified citric acid (Cit) wrapped NaYF4:Yb/Er-Cit-CD (Y:Yb/Er-Cit-CD) up-conversion nanocomposite has been synthesized, which emits green fluorescence at 550 nm under 980 nm near-infrared (NIR) excitation. In the presence of oxidized 3, 3′, 5, 5′-tetramethylbenzidine (oxTMB), the green fluorescence is significantly quenched attributed to the fluorescence inner filter effect (IFE) between oxTMB and Y:Yb/Er-Cit-CD. When RA is intervened, blue oxTMB is reduced to colorless 3, 3′, 5, 5′-tetramethylbenzidine (TMB) inducing the recovery of up-conversion fluorescence. At the same time, colorimetric and photothermal signals readout can be easily achieved thanks to the color indication and photothermal effect of the oxTMB. The constructed Y:Yb/Er-Cit-CD/oxTMB sensor displays high sensitivity, visibility and simplicity for RA, and the limits of detection (LOD) for fluorescence, colorimetric and photothermal were 0.004 µmol/L, 0.036 µmol/L and 0.043 µmol/L, respectively. This sensing system is successfully performed for the detection of RA in food samples.
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