Latest ArticlesA wavelength-dependent three-dimensional (3D) superlocalization imaging method on gold nanoislands (GNIs) chip was developed as a supersensitive single-molecule thyroid-stimulating hormone (TSH) nanobiosensor. Scattered and fluorescent signals from gold nanoislands on the substrate and quantum dots (QDs) nanoprobes were simultaneously isolated and acquired within an evanescent field layer generated by total internal reflection (TIR) of incident light using a dual-view device. The 3D TIR fluorescence images of TSH-bound QDs on the GNIs were obtained using z-axis optical sectioning at 10 nm intervals before/after immunoreaction to identify the optimal conditions for detection. The localized centroid position of QD nanoprobes and GNI were distinguished at a subdiffraction limit resolution using 3D Gaussian fitting to the point spread function. The QD TSH nanobiosensor using wavelength-dependent 3D TIR fluorescence-based single-molecule localization microscopy (3D TIRF-SLM) imaging technique showed an excellent detection limit of 90 yoctomoles (~54 molecules) and a wide linear dynamic range of 1.14 zmol/L − 100 pmol/L for TSH. The detection sensitivity was about 4.4 × 109 times higher than conventional enzyme-linked immunosorbent assay and could successfully quantify TSH in human serum. The wavelength-dependent 3D TIRF-SLM technique may emerge as a reliable platform for ultrahigh-sensitive nanobiosensors at the single-molecule level and early diagnosis with quantification of disease-related ultra-trace biomolecules.
Direct synthesis of glycerol carbonate (GC) from CO2 and glycerol (a byproduct of biodiesel production) is a route to obtain a high-value chemical from waste and low-cost byproducts but has not yet industrialized due to the lack of efficient catalysts. Ceria (CeO2) exhibits the highest catalytic activity and GC selectivity among the heterogeneous catalysts studied so far. However, the mechanism of this reaction over CeO2 catalysts has not been studied in detail. Herein, we synthesized CeO2 nanocrystals with different morphologies as model catalysts that can predominantly expose {111}, {110}, and {100} facets, and their surface acid-base properties were characterized using high-sensitivity temperature-programmed desorption of NH3 and CO2 with quadrupole mass spectrometry as detector (NH3-TPD-QMS and CO2-TPD-QMS). We found that the catalytic performance (GC formation rate) is strictly linearly dependent on the density of basic sites, which is relevant to the adsorption and activation of CO2. In addition, to illustrate a more microscopic reaction mechanisms underlying the formation of GC from CO2 and glycerol on all three low-index surfaces (111), (110) and (100), we also performed comprehensive first principles calculations. A three-step Langmuir–Hinshelwood (LH) mechanism was identified in which the annulation reaction is the rate-limiting step. The CeO2 (111) surface exhibits the lowest overall activation energy, which agrees well with the catalytic performance that the CeO2 nano-octahedra, predominantly exposing {111} facets, have the highest GC formation rate. This work is the first to combine experiments on shaped CeO2 model catalysts with first-principles calculations to gain insight into the mechanism of direct synthesis of GC from CO2 and glycerol, and will aid in the development of catalysts with improved performance.
Rational design of heterogeneous catalysts with high activity and stability is crucial in peroxymonosulfate (PMS)-based oxidation treatment of wastewater. Herein, the graphite oxide-cobalt ferrite (GO-CoFe2O4) composite was constructed, and its morphological, component and structural characteristics were thoroughly examined, respectively. GO-CoFe2O4 obviously boosted PMS catalytic performance on di-n–butyl phthalate removal (DBP, RDBP = 90%, RTOC = 37%), which indicated by the first-order kinetic constant (kDBP = 0.060 min−1) being roughly 4 times than pure CoFe2O4 (kDBP = 0.015 min−1). The fabrication of GO-CoFe2O4 brought the favorable stability and repeatability up to six cycles. Moreover, the method of batch dosing catalyst was creatively proposed to improve the PMS utilization efficiency. The coupling of GO enhanced the dispersion of CoFe2O4 particles to obtain sufficient active sites, additionally, the plentiful C=O groups and free-flowing electrons on GO promoted GO-CoFe2O4 to coordinate a redox process during PMS activation. With the aid of theoretical calculations, GO-CoFe2O4 was revealed to exhibit a strong affinity toward PMS adsorption, where PMS spontaneously dissociated into sulfate radical (SO4•−), hydroxyl radical (•OH) and singlet oxygen (1O2), acting as the reactive oxygen species (ROSs). Electrons cycling between Co, Fe and O species ensured continuous ROSs generation and excellent catalytic performance.
A new palladium-catalyzed annulative allylic alkylation (AAA) reaction of 2-(indol-2-yl)phenols with dual allylic electrophiles such as isobutylene dicarbonate and butene dicarbonate is described, leading to the regioselective synthesis of tetracyclic medium-sized cyclic ethers possessing a bridged aryl-indole scaffold, namely, benzo[2,3]oxocino[4,5-b]indoles and benzo[2,3]oxepino[4,5-b]indoles, in good to excellent yields. This protocol demonstrates a broad substrate scope, good compatibility with substituents and high regioselectivity, providing a catalytic and flexible method for creating bridged aryl-indole skeletons.
Accurate and sensitive detection of cancer cells is of significant importance for early diagnosis and treatment of cancer. Here, we developed an extracellular ATP-activated hybridization chain reaction (HCR) amplification strategy to meet this purpose. This strategy relies on three DNA probes, Apt-trigger, H1-ATP aptamer duplex and hairpin H2. The Apt-trigger probe consists of two components: an aptamer sequence for specific recognition of the target cells, and a trigger sequence for the HCR assembly. The duplex structure of H1-ATP aptamer causes the toehold in hairpin H1 to be hidden, preventing the strand-displacement reaction between hairpin H1 and Apt-trigger. Upon activation with ATP, the ATP aptamer will bind to ATP to dissociate from hairpin H1, thus leading to an Apt-trigger-induced strand-displacement reaction and subsequent HCR with hairpin H2 on the target cell surface. Benefiting from aptamer recognition and ATP-activated HCR amplification, this strategy can not only perform sensitive quantitative analysis with a detection limit of 25 cells in 200 µL of binding buffer, but also show desirable specificity and accuracy for identifying target cells from control cells and mixed cell samples. Importantly, this method retains stable and good performance for target cell detection in 10% fetal bovine serum, demonstrating great potential for clinical diagnosis in complex biological matrices. Furthermore, this strategy can be adapted to detect various types of cancer cells by changing the corresponding aptamer sequence.
Manganese oxides show a strong catalytic activity in the peroxymonosulfate (PMS) advanced oxidation process but have poor chemical stability and a propensity to cause the aggregation of nanoparticles. Here, a novel composite material (abbreviated as MnOx@ACF) was synthesized, characterized, and applied. Activated carbon fiber (ACF) was selected as a carrier, which modulated the composition of manganese oxides. The results showed that MnOx@ACF had a strong adsorption ability and successfully activated PMS to degrade tetracycline hydrochloride (TCH), with a removal efficiency of 89.0% in 30 min. Influencing factors such as pH and coexisting ion species were investigated, and a five-cycle test was conducted. Singlet oxygen (1O2) was predominated in the MnOx@ACF/PMS system. A possible explanatory pathway of TCH was proposed based on the results of the high performance liquid chromatography-mass spectrometry. It was concluded that this study provides a novel insight into the activation of PMS for the degradation of organic matter by carbon-loaded multivalent manganese oxides.
This work reported a facile approach to surface oxygen vacancy (OV)-enriched urchin-like TiO2 microparticles (U-TiO2), which were highly effective and durable in catalyzing selective nitrate reduction to ammonia (NO3RR). Specifically, the U-TiO2 delivered a mass activity of 1.15 min−1 mgcatalyst−1, a low yield of toxic NO2−-N intermediate (≤0.4 mg/L) and an exceptional high NH3-N selectivity of 98.1% in treating 22.5 mg/L of NO3−-N under a potential of -0.60 V vs. RHE, outperforming most of the reported oxide-based catalysts. When comparing the performance of U-TiO2 with that of the solid amorphous TiO2 counterpart (A-TiO2) that had close particle size but more OV on surfaces, we identified that the OV was the reactive sites, but rather than its content, the NO3RR kinetics were primarily limited by the electron and mass transfer at U-TiO2/water interfaces. Accordingly, the superior performance of U-TiO2 to A-TiO2 could be ascribed to the hierarchical urchin-like structure in U-TiO2. The in-situ DEMS test revealed that the NO3RR on U-TiO2 followed a pathway of *NO3− → *NO2−→ *NO → *N → *NH → *NH2 → *NH3. We also demonstrated that the U-TiO2 could keep its robust performance under a wide NO3−-N concentration range and in the presence of some co-existing ions (such as Ca2+, Cl−, Mg2+). However, the presence of humic acid and CO32− in water slowed down the NO3RR on U-TiO2. This work provides a more fundamental insight into the OV-driven NO3RR process on TiO2, which should benefit for the development of efficient TiO2-based catalysts.
Herein, we review the significant of ordered macroporous (OM) TiO2-based catalysts for boosting photocatalytic CO2 reduction. Based on the need to improve the three key factors of photogenerated charge separation efficiency, solar energy utilization and CO2 adsorption rate during the conversion of CO2 to H2O, we summarized five modification measures: including doping ions into OM TiO2, introducing second semiconductor coupling and noble metal nanoparticles for fabricating multiple Z-scheme heterojunctions, constructing hierarchical pore and carbon-loaded OM TiO2 materials, which effectively enhance the absorption rate of visible light, the separation rate of electrons-hole pairs and the selection of multiple active sites. The OM structured TiO2-based photocatalysts solve the single or multiple key factors for enhancing photocatalytic performances during CO2 conversion. The catalytic mechanism and pathways of OM structured TiO2-based photocatalysts for CO2 reduction are discussed and summarized. It provides new insights on the development of high-efficient catalyst for photocatalytic CO2 conversion to solar fuels.
A flexible organic artificial synapse (OAS) for tunable time-frequency signal processing was fabricated using a tri-blend film that had been fabricated using a one-step solution method. When combined with a chitosan film, this OAS can achieve an ultrashort-term retention time of only 49 ms for instant electrical-computing applications; this is the shortest retention time yet achieved by a two-terminal artificial synapse. An array of these flexible OASs can withstand a high bending strain of 5% for 104 cycles; this deformation endurance is a new record. The OAS was also sensitive to the number and frequency of electrical inputs; a tunable cut-off frequency enables dynamic filtering for use in image detail enhancement. This work provides a new resource for development of future neuromorphic computing devices
There are some critical issues hindering the practical applications of aqueous zinc-ion batteries (ZIBs), although they possess high safety and low cost as one of promising energy storge devices, such as the Zn dendrite growth and the by-product of Zn4SO4(OH)6·xH2O (ZHS) resulted from some side reactions in a mild electrolyte. Herein, a compact and self-repairing solid electrolyte interface (SEI) film, as labeled the PVDF-Zn(TFSI)2-ZHS coating [The PVDF and Zn(TFSI)2 are polyvinylidene fluoride and zinc bis(trifluoromethanesulfonyl)imide, respectively], which turns the in-situ generated ZHS into a beneficial ingredient onto the pre-coated PVDF-based composite coating layer containing Zn(TFSI)2, was designed and fabricated by a simple doctor blade method. It is shown that the SEI layer can effectively isolate Zn from the electrolyte and homogenize the Zn2+ flux, and thus effectively suppress side reactions and dendrites growth. Benefiting from the hybrid SEI layer, a symmetric cell exhibits a high cycling stability over 750 h at 2.0 mA/cm2 and 2.0 mAh/cm2, and meanwhile, a full-cell, coupled with K+ pre-intercalation α-MnO2 (KMO) cathode, displays excellent rate performance, stable coulombic efficiency and an acceptable cycle life. This work provides a feasible approach for simple and scalable modification of Zn anodes to achieve high performance.
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