Summary The use of low‐rank coal in a clean and efficient manner is a major challenge facing the current coal technology. A high‐sulfur coal with 4.5 wt% sulfur is chosen to examine the compatibility of the pristine coal and the purified contrast with a solid oxide fuel cell (SOFC) with nickel cermet anodes. Desulfurization of the pristine coal is performed by molten caustic leaching method with a removal ratio of 80%. Analyses of the physicochemical properties of coal samples indicate that the purified coal has a more favorable structure and higher Boudouard reactivity, which is suitable as a fuel for fuel cells. The assessment of electrochemical performance reveals that the purification treatment not only makes the peak power density of SOFCs improve from 115 to 221 mW cm−2 at 900°C but also extends their durability from 1.7 to 11.2 hours under a current density of 50 mA cm−2 at 850°C with a fuel availability increasing from 6.25% to 40%. The postmortem analyses show that far less deposited carbon and nickel sulfide are observed on the anode surface. The fuel‐based investigation reveals that the purified coal is a promising fuel for direct carbon fuel cells.
Biomedical applications and biomarkers for early clinical diagnostics and the treatment of diseases demand efficient and selective enrichment platforms for glycoproteins.
The detection and adsorption of nitroaromatic compounds such as 2,4-dinitrotoluene (DNT) is of great importance, but the selective detection of trace DNT in water remains a challenge. Here, we report molecularly imprinted polymer (MIP) nanofibers fabricated by electrospinning using DNT as a template molecule and poly(allylamine) as a functional macromer. The physical and chemical properties of the nanofibers were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), and the DNT adsorption and selectivity properties were also studied by high performance liquid chromatography (HPLC). The results show that the nanofibers prepared using 20 wt% poly(ethylene terephthalate) (PET) in solvent had a good morphology and an optimal ratio of poly(allylamine) and DNT, and the imprinted nanofibers showed specific adsorption of DNT, in accordance with the Freundlich isotherm model and Scatchard analysis. Furthermore, the imprinted nanofibers showed remarkable stability and reusability, losing only 3% of their performance after eight cycles. Thus, the imprinted nanofibers fabricated by this strategy could be used for trace DNT extraction, separation, and further construction of sensors in the near future.
Dendritic fibrous nanosilica (DFNS) has very high surface area and well-defined nanochannels; therefore, it is very useful as supporting material for numerous applications including catalysis, sensing, and bioseparation. Due to the highly restricted space, addition of molecular ligands to DFNS is very challenging. This work studies how ligand conjugation in nanoscale pores in DFNS can be achieved through copper-catalyzed click reaction, using an optional, in situ synthesized, temperature-responsive polymer intermediate. A clickable boronic acid is used as a model to investigate the ligand immobilization and the molecular binding characteristics of the functionalized DFNS. The morphology, composition, nanoscale pores, and specific surface area of the boronic acid functionalized nanosilica were characterized by electron microscopy, thermogravimetric and elemental analysis, Fourier transform infrared spectroscopy, and nitrogen adsorption–desorption measurements. The numbers of boronic acid molecules on the modified DFNS with and without the polymer were determined to be 0.08 and 0.68 mmol of ligand/g of DFNS, respectively. We also studied the binding of small cis -diol molecules in the nanoscale pores of DFNS. The boronic acid modified DFNS with the polymer intermediate exhibits higher binding capacity for Alizarin Red S and nicotinamide adenine dinucleotide than the polymer-free DFNS. The two types of boronic acid modified DFNS can bind small cis -diol molecules in the presence of large glycoproteins, due in large part to the effect of size exclusion provided by the nanochannels in the DFNS.
A simple, sensitive, and straightforward method is developed to study the process of molecular imprinting via real-time fluorescence measurements. The imprinted polymer can be used to remove ARS from water, and as a fluorescent probe to detect Cu2+.
An analytical method is developed for ultrasensitive detection of citrinin using double isothermal amplification and CRISPR-Cas12a. Gold nanoparticles (AuNPs) modified with antigen and thiol-terminated, single-strand DNA (ssDNA) are used as a probe. The antigen-modified AuNPs compete with citrinin to bind to magnetic beads coated with an anticitrinin antibody. After a simple magnetic separation, the AuNPs are collected, and the ssDNA are released after they are washed with a dithiothreitol solution. The ssDNA is first amplified by an exponential amplification reaction and then used as a primer in a subsequent hybridization chain reaction to produce double-stranded DNA (dsDNA) that contains a protospacer adjacent motif to allow recognition by CRISPR-Cas12a. The dsDNA activates the Cas12a-gRNA to cleave a reporter ssDNA to generate a fluorescence signal. The developed analytical method has a low detection limit (0.127 ng mL −1 ) and a wide linear range (0.005−500 μg mL −1 ) for detection of citrinin. For detection of citrinin in oat and flour, recoveries of 97−104% and 105−111% are obtained, respectively. By combining double isothermal amplification with CRISPR-Cas12a, ultrahigh sensitivity and selectivity can be achieved for detection of toxins in food.
A novel dual-amplification system based on CRISPR-Cas12a and horseradish peroxidase (HRP) was developed for colorimetric determination of MC-LR. This dual-amplification was accomplished by combining the nuclease activity of CRISPR-Cas12a with the redox activity of HRP. HRP linked to magnetic beads through an ssDNA (MB-ssDNA-HRP) was used to induce a color change of the 3,3′,5,5′-tetramethylbenzidine (TMB)-H2O2 chromogenic substrate solution. Specific binding of MC-LR with its aptamer initiated the release of a complementary DNA (cDNA), which was designed to activate the trans-cleavage activity of CRISPR-Cas12a. Upon activation, Cas12a cut the ssDNA linker in MB-ssDNA-HRP, causing a reduction of HRP on the magnetic beads. Consequently, the UV–Vis absorbance of the HRP-catalyzed reaction was decreased. The dual-signal amplification facilitated by CRISPR-Cas12a and HRP enabled the colorimetric detection of MC-LR in the range 0.01 to 50 ng·mL−1 with a limit of detection (LOD) of 4.53 pg·mL−1. The practicability of the developed colorimetric method was demonstrated by detecting different levels of MC-LR in spiked real water samples. The recoveries ranged from 86.2 to 118.5% and the relative standard deviation (RSD) was 8.4 to 17.6%. This work provides new inspiration for the construction of effective signal amplification platforms and demonstrates a simple and user-friendly colorimetric method for determination of trace MC-LR. Graphical Abstract
Hybridization chain reaction (HCR)-based amplification strategies have shown excellent prospects of application in detection thanks to its non-enzymatic and isothermal features. For protein biomarker detection, most bioanalytical assays are dependent on antibodies or aptamers to provide specific recognition to allow single strand DNA (ssDNA) to initiate specific HCR to realize effective signal amplification. Molecularly imprinted polymers (MIPs) are excellent alternative molecular recognition materials because of low cost and high stability. In this work, we developed a non-enzymatic, HCR-amplified protein detection/ quantification using MIP as a recognition element for hemoglobin (Hb). The MIP was prepared by Pickering emulsion polymerization using mesoporous silica nanoparticles as a stabilizer, producing surface-accessible binding sites for Hb. To demonstrate specific detection of proteins, Hb captured by the MIP beads was reacted with a ssDNA to add the initiator sequence of the HCR to the captured protein in situ. After addition of two hairpin DNA molecules that were labeled with fluorophores and quenchers, the HCR reaction took place and led to the opening of the hairpins and formation of nicked dsDNA, with concomitant emission of fluorescence. A linear relationship between fluorescence intensity and the logarithm protein concentration in the range of 0.01−1 mg/mL was obtained. The limit of Hb detection was as low as 0.006 mg/mL. In addition, the non-enzymatic, isothermal fluorescent detection exhibited high selectivity, satisfactory recovery, and good repeatability. This work opens possibilities of using MIP and nucleic acid amplification to achieve low-cost, simple, and reliable detection and quantification of protein biomarkers.
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