Latest ArticlesEnzyme assisted DNA probes are powerful tools in molecular diagnostics for their simplicity, rapidity, and low detection limit. However, cost of probes, difficulty in optimization and disturbance of secondary structure hindered the wider application of enzyme assisted DNA probes. To solve the problems, we designed a new system named shared-probe system. By introducing two unlabeled single stranded DNA named Sh1 and Sh2 as the bridge between probe and the substrate, the same sequence of dually labeled probe with stable performance was shared for different mutations, thus sparing the expense and time cost on designing, synthesizing and optimizing corresponding probes. Besides, the hybridization between Sh1 and the substrate could overcome secondary structures, which guaranteed the detection of different substrates. The performance and generality of the design were tested by low abundance detection in synthetic single DNA samples and the limit of detection was 0.05% for PTENR130Q, EGFR-L858R and 0.02% for BRCA1-NM007294.3. In genomic DNA samples, the limit of detection of 0.1% can be achieved for EGFR-L858R, demonstrating the potential of clinical application in our design.
Several 2D nanosheets of porphyrin MOFs with various transition-metal clusters as metal nodes were prepared via a simple solvothermal method to apply in the photocatalytic hydrogen evolution, in which the hydrogen production rate of the optimal NS-Cu was as high as 15.39 mmol g−1 h−1. A series of experimental technologies especially cyclic voltammetry (CV) and Mott-Schottky (M-S) had been adopted to investigate the charge-transfer property of photo-generated electron-hole pairs, it was found that the uniformly dispersed Cu-clusters nodes in the original 2D MOFs played a key role in the electron transfer process, that was, the photo-generated electron transferred from excited state eosin-Y to the Cu-clusters nodes for the efficient hydrogen evolution. The excellent photocatalytic performance could be attributed to the reversible oxidation-–reduction process of CuⅡ/CuⅠ, which had excellent electron-receiving and electron-outputting capabilities. Our results provided a novel avenue to adapt the uniformly dispersed metal nodes in the original MOFs as cost-effective noble-metal-free cocatalysts with very high atom-utilization efficiency to improve the photocatalytic hydrogen evolution performance in dye-sensitized system.
Conversion of hexavalent chromium (Cr(Ⅵ)) to trivalent chromium (Cr(Ⅲ)) is an effective way to reduce its environmental risk, especially via photoreduction process. However, over a wide range of pH values, it is still a great challenge to achieve a high removal rate, and the disposal of produced Cr(Ⅲ) should be concerned. In this work, we implemented a high removal rate at 98% for Cr(Ⅵ) and total chromium (Cr(T)) over a wide pH range (4–10) through the synergistic effect of adsorption, photoreduction and immobilization on the surface of BiOBr0.25I0.75. The substitution of bromine by iodine reduced the adsorption energy of Cr(Ⅵ) on BiOBr0.25I0.75, promoting the adsorption of Cr(Ⅵ). Meanwhile, the introduced iodine upshifted the conduction band (CB), enhancing the reduction ability for Cr(Ⅵ) to Cr(Ⅲ). The negative surface of BiOBr0.25I0.75 can capture Cr(Ⅲ), achieving a high removal rate for Cr(T). The pH-independent feature for Cr(Ⅵ) and Cr(Ⅲ) removal make BiOBr0.25I0.75 a potential material for chromium-containing wastewater treatment. This work provides an effective strategy for removing chromium over a wide pH range.
Owing to the exorbitant overpotential and serious carrier recombination of graphitic carbon nitride (g-C3N4), noble metal (NM) is usually served as the H2 evolution co-catalyst. Although the NM (such as Pt) nanoparticles can reduce the H2 evolution overpotential, the weak van der Waals interaction between Pt and g-C3N4 makes against the charge transfer. Herein, the solvothermal method is developed to achieve semi-chemical interaction between Pt and g-C3N4 nanotube (Pt-CNNT) for fast charge transfer. Moreover, the generated in-plane homojunction of CNNT can accelerate charge separation and restrain recombination. Meanwhile, the metallic Pt is an excellent H2 evolution co-catalyst. Photo/electrochemical tests verify that the semi-chemical interaction can improve photogenerated charge separation and transferability of CNNT. As a result, the photocatalytic H2 evolution turnover frequency (TOF) of Pt-CNNT under visible light irradiation reaches up to 918 h−1, which is one of the highest in the g-C3N4-based photocatalysts. This work provides a new idea to improve the charge transfer for efficient photocatalytic H2 evolution.
The catalytic elimination of nitrogen-containing volatile organic compounds (NVOCs) still encounters bottlenecks in NOx formation and low N2 selectivity. Here, a series of Cu-promoted Ce-Zr mixed oxide catalysts were synthesized using a simple precipitation approach, and n-butylamine was adopted as the probe pollutant to evaluate their catalytic performance. The CeCu10%ZrOx catalyst exhibited the best catalytic activity, with 100% n-butylamine conversion and 90% N2 selectivity at 250 ℃. Concurrently, this sample also displayed good water resistance. A detailed characterization of the catalyst was performed through a series of experimental studies and theoretical calculations. The addition of Cu increased the redox property and promoted the production of oxygen vacancies, all of which were favorable for the greatest n-butylamine selective catalytic oxidation performance. The changes of oxygen vacancies over CeCu10%ZrOx in reaction process were studied by in situ Raman spectra. Moreover, in situ diffuse reflectance infrared Fourier transform spectra (DRIFTs) and theoretical calculations were employed to explore the reaction mechanism of n-butylamine selective oxidation. The high activity and selectivity of this catalyst confirm the practical feasibility of the selective oxidation of n-butylamine to CO2 and N2, and the exploration of the reaction mechanism provides new insights into the further design of catalysts.
An efficient photo-Fenton catalyst (FeS2@HTCN) was designed by maximizing the synergistic effect of FeS2 nanoparticles and hollow tubular g-C3N4 (HTCN). Molecule self-assembly and molten salts-assisted calcination were used to engineering the hollow structured g-C3N4 before anchoring FeS2 nanoparticles on the walls of HTCN via reflux method. Compared to bulk g-C3N4, the unique structure of HTCN and heterojunction in the composite endowed FeS2@HTCN with more active sites and abundant channels for electron transfer and charge separation. The enriched electrons can improve the Fe3+ recycling and boost Fe2+ catalyzed •OH production via H2O2. As-prepared photo-Fenton catalyst was successfully applied to the treatment of industrial paint wastewater. The paint wastewater with its COD as high as 8200 mg/L can be effectively degraded with 0.2 mol/L H2O2 in 90 min under visible light irradiation. The photo-Fenton system was further evaluated according to the process stability and economic benefit, proving that the strategy presented in this work would be applicable to the treatment of real wastewater.
A gold nanoparticle (AuNP) aggregation-induced colorimetric aptasensing method for quantitative detection of sulfadimethoxine (SDM) with a smartphone was developed. AuNPs were complexed with aptamers which protected AuNPs from aggregating in high-concentration salt solutions. In the presence of SDM, SDM bound with the aptamer on the surface of AuNPs with higher affinity, which competitively desorbed the aptamer from the AuNP surface and resulted in AuNPs aggregation, accompanied with a color change from red to purple-blue. The R, G and B values of images taken by a smartphone camera were analyzed with an app on the smartphone, and were utilized for quantitative analysis of SDM. Under the optimized conditions, the colorimetric aptasensing method using a smartphone showed high sensitivity for SDM, with the limit of detection of 0.023 ppm, lower than the allowed maximum SDM residue limit. This study provides a simple, fast, and easy to read method for on-site quantitative biochemical and cellular analysis.
Microfluidic devices have become a powerful tool for chemical and biologic applications. To control different functional parts on the microchip, valve plays a key role in the device. In conventional methods, physio-mechanical valves are usually used on microfluidic chip. Herein, we reported a chemo-mechanical switchable valve on microfluidic chip by using a thermally responsive block copolymer. The wettability changes of capillary with copolymer modification on inner surface were investigated to verify the function as a valve. Capillaries with modification of poly-(N-isopropylacrylamide-co-hexafluoroisopropyl acrylate) (P(NIPAAm-co-HFIPA)) with a 20% HFIPA was demonstrated capable of control aqueous solution stop or go through. Then short capillaries with copolymer modification were integrated in microchannels as valves. With the temperature changing around lower critical solution temperature (LCST), the integrated chemo-mechanical switchable valve exhibited excellent "OPEN–CLOSE'' behavior for microflow control. After optimization of the block copolymer sequences and molar ratio, a switching time as low as 20 s was achieved. The developed micro valve was demonstrated effective for flow control on microchip.
Mn-Si-MEL zeolite was developed as a bi-functional adsorption-catalytic oxidation material for volatile organic compounds (VOCs) elimination due to its good hydrophobicity & good organophileproperty brought by the substitution of Mn for Al in zeolite and the superior catalytic oxidation property endowed by the existence of Mn species. Various Mn-Si-MEL samples were obtained by introducing Mn to MEL crystallization system via different ways. It was found the incorporated Mn ways have a significant effect on the behavior of Mn being involved in the crystallization of MEL and finally influenced the distribution of Mn in zeolite as well the physicochemical properties of product zeolite. The seeding method (Mn-S2(Seed)) is favorable for the good incorporation and uniform distribution of Mn in zeolite while both recrystallization method (Mn-S2(RC)) and direct synthesis method (Mn-S2(DH)) are favorable for obtaining more reducible Mn species and surface adsorbed oxygen species. The Mn amount incorporated into zeolite follows Mn-S2(RC) (1.96 wt%) > Mn-S2(Seed) (1.07 wt%) ≈ Mn-S2(DH) (0.97 wt%), the adsorption capacity of various samples follows Mn-S2(Seed) (83.3 μmol/g) ≈ Mn-S2(RC) (82.1 μmol/g) > Mn-S2(DH) (76.1 μmol/g), while the catalytic oxidation ability of three samples follows Mn-S2(RC) ≈ Mn-S2(DH) > Mn-S2(Seed). Furthermore, Mn-S2(RC) which exhibits both superior adsorption capacity and catalytic oxidation ability shows good hydrophobicity and superior recyclability, demonstrating its great potential to be applied in the VOCs elimination by an enrichment-degradation route.
The cellular response to the complex extracellular microenvironment is highly dynamic in time and type of extracellular matrix. Accurately reconstructing this process and analyzing the changes in receptor conformation on the cell membrane surface and intracellular or intercellular signaling has been a major challenge in analytical chemistry and biophysical methodology. In this paper, a time-coded multi-concentration microfluidic chemical waveform generator was developed for the dynamic signaling probing with single-cell array of high temporal resolution, high throughput, and multi-concentration combination stimulation. Based on innovative microchannel structure, sophisticated external control methods and multiplexing technology, the system not only allowed for temporally sequential permutations of the four concentrations of stimuli (time code), but also generated pulsed and continuous waveforms at different frequencies in a highly controllable manner. Furthermore, the single-cell trap array was set up to efficiently capture cells in suspension, dramatically increasing throughput and reducing experiment preparation time. The maximum frequency of the platform was 1 Hz, and one cell could be stimulated at multiple frequencies. To show the ability of the system to investigate rapid biochemical events in high throughput, pulse stimulation and continuous stimulation of different frequencies and different time codes, combined with four concentrations of histamine (HA), were generated for probing G protein-coupled receptor (GPCR) signaling in HeLa cells. Then, statistical analysis was performed for the mean peak height and mean peak area of the cellular response. We believe that the time-coded multi-concentration microfluidic chemical waveform generator will provide a novel strategy for analytical chemistry, biophysics, cell signaling, and individualized medicine applications.
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