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Efficient signal amplification is essential to construct ultrasensitive biosensors for biologically relevant species with abundant concomitant interferences. Here, we apply LbaCas12a as a signal amplifier to develop a versatile CRISPR-Cas12a platform to detect a wide range of analytes in ultralow concentrations. The platform relies on the indiscriminate single-stranded DNase activity of LbaCas12a, which recognizes single-stranded DNA intermediates generated by non-DNA targets down to femtomolar concentrations and subsequently enhances the fluorescence signal output. With the help of functional nucleotides (DNAzyme and aptamer), ultrasensitive bioassays for Pb2+ and Acinetobacter baumannii have been designed with a limit of detection down to ∼0.053 nM and ∼3 CFU/mL, respectively. It also allows simultaneous detection of four microRNAs (miRNAs) at a picomolar concentration without significant interferences by other counterparts, suggesting the potential of multiplexed miRNA expression profiles analysis in high throughput. Given the versatility and generality of the CRISPR-Cas12a platform, we expect the current work to advance the application of CRISPR-Cas-based platforms in bioanalysis and provide new insights into ultrasensitive biosensor design.

Tc play an important role in U/Pu partition when U(IV) is used as reducing agent in PUREX process. In this work, U/Pu partition flowsheet experiments were studied using different organic reducing agents, which included N,N-dimethylhydroxylamine (DMHAN)–methylhydrazine (MMH), acetohydroxamic acid (AHA) and dihydroxyurea (DHU). The results showed very good U/Pu partition performance in the presence of Tc, which mean Tc would not cause major malfunctions in the U/Pu partition operation with these reducing agents. The technetium fractions distributed in the products was mainly attributed to Tc(VII) reduction kinetics with different reducing agents.

Herein, we combined toehold exchange with ligation-free rolling circle amplification (RCA) by programming nucleolytic conversion of hairpin probe into sensors, allowed for both high specific recognition and universal signal amplification for RNA detection. The rational engineered HP ensured highly specific recognition based on toehold exchange and allowed the pre-formed circular template for RCA to be shared for different RNAs detection. Generally, detecting different RNA requires different circular template for signal amplification. In this paper, the circular template for RCA was independent of the sequences of the target, so the signal amplification system was an universal one for different RNAs detection. Taking miRNA let-7d as a model target, this method showed a wide linear range from 1 fM to 1 nM with a detection limit of 0.46 fM and exhibited a remarkable selectivity even in distinguishing homologous miRNAs with 1-nt or 2-nt difference. To evaluate the potential of the method, it was applied to analysis the let-7d concentration in human serum, total RNA, and cell lysates. In conclusion, we believe this method exhibits potential for both specific discrimination and universal signal amplification for RNA analysis in complex matrices.

Multifunctional nano-materials that can be used to monitor the expression of specific biomarkers and serve as vehicles for controlled drug delivery are highly desirable. Herein, we report a new DNA-hybrid-gated core–shell upconversion nanoprobe (UCNP@MOF/DOX) for fluorescence analysis of microRNA-21 (miR-21), which also triggers the release of drug loaded in the probes for on-demand anti-cancer treatment. The nanoprobe is built on the merits of ultraviolet-visible light of upconversion nanoparticles (UCNPs) excited by near-infrared (NIR) and extraordinary loading capability of metal–organic frameworks (MOFs) for drug delivery. Controlled release of doxorubicin (DOX) from the nanoprobe by miR-21 underwent the following two-stage kinetics: a fast release stage specifically triggered by miR-21 and proportional to miR-21 concentration and a slow stage observed in both gated and ungated nanoprobes due to collapse of the UIO-66-NH2 coatings via ligand exchange with phosphates. In addition, the nanoprobe showed good selectivity, a linear response towards miR-21 ranging from 4 nM to 500 nM, and a limit of detection in 4 nM, which precluded unintended payload leakage due to low-abundance endogenous miR-21 expression in normal cells. Moreover, based on a dual-targeted delivery system constituted by AS1411-mediated recognition and responsive release of DOX, a specific cytotoxic efficacy was observed in MCF-7 cells. The present work provides a smart and robust nanoprobe for real-time detection of miRNA and dual-responsive drug delivery in tumor cells.

A fluorometric assay was introduced to determine Acinetobacter baumannii (A. baumannii) in blood samples by utilizing Zr-MOFs both as functional coating for magnetic Fe3O4 nanoparticles to provide modification surface (Zr-mMOF) and as fluorescein carrier to produce fluorescence signals (F@UIO-66-NH2). Through strong Zr-O-P bonding, two distinct terminal phosphate-labeled A. baumannii and lipopolysaccharide (LPS) specific aptamers were attached onto Zr-MOFs to fabricate the magnetic core-shell capture probe (denoted as Zr-mMOF-p-Ab-Apt) and signal probe (denoted as F@UIO-66-NH2-p-LPS-Apt), respectively. After successive incubation with A. baumannii in blood samples and magnetic separation, the sandwich-type composite of capture probe/A. baumannii cells/signal probe was treated with high concentration of anionic phosphate ions to destroy the nano-structure of UIO-66-NH2 in the signal probe and fast release of fluorescein to produce amplified fluorescence signals. Due to the high aptamer modification efficiency of Zr-mMOF-p-Ab-Apt (up to 93%) and its strong affinity to A. baumannii, the enrichment efficiency of this capture probe has reached to 96.7%. Further, due to the high fluorescein loading efficiency of UIO-66-NH2 and our novel amplification strategy to destroy F@UIO-66-NH2-p-LPS-Apt to release and amplify fluorescein signals at 512 nm in the presence of high concentration of anionic phosphate ions, the sensitivity of this method has reached 10 cfu mL−1. This method allows enrichment and determination of A. baumannii within ~2.5 h. The limit of detection of A. baumannii in blood samples is 10 cfu mL−1 with a linear range of 101–105 cfu mL−1. This indicates the potential of this assay for diagnosis of bloodstream infection in early stage.

N6-methyladenosine (m6A), one of the most abundant RNA methylation which is ubiquitous in eukaryotic RNA, plays vital roles in many biological progresses. Therefore, the rapid and accurate quantitative detection of m6A is particularly important for its functional research. Herein, a label-free and highly selective electrochemical immunosensor was developed for the detection of m6A. The method is established on that the anti-m6A-Ab can recognize both m6A-RNA and m6A-DNA. An analogous modified DNA probe (L1) serves as a signal molecule, by competing with m6A-RNA for binding to Abs to broaden the linear range. The detection of m6A-RNA by this method is unaffected by the lengths and base sequences of RNA. Under optimal conditions, the proposed immunosensor presented a wide linear range from 0.05 to 200 nM with a detection limit as low as 0.016 nM (S/N = 3). The specificity and reproducibility of the method are satisfactory. Furthermore, the developed immunosensor was validated for m6A determination in human cell lines. Thus, the immunosensor provides a promising platform for m6A-RNA detection with simplicity, high specificity and sensitivity.

The performance of a series of novel O-phenoxydiamides extracting Zr(IV), Eu(III), U(VI), Pu(IV) and Am(III) was studied. The result of extraction experiments showed that the coordination abilities of these five congeneric O-phenoxydiamides decrease in the order of CycleDODA > PhenylDODA > ButylDODA > HexylDODA > BenzoDODA, the abilities of different metal ions coordinating with the same ligand decrease in the order of Pu(IV) ≫ U(VI) > Zr(IV), Eu(III), Am(III). At HNO3 concentration of 5.0 mol/L, the distribution ratio of BenzoDODA/n-dodecane extracting Pu(IV) is much larger than those of other metal ions, the separation factors of Pu(IV) over Eu(III), Zr(IV), U(VI) and Am(III) are between 20 and 300, which can be used for recovering Pu(IV) selectively from highly acidic liquid waste. The density functional theory (DFT) calculation of the 25 complexes in geometrical structure, Mayer bond order (MBO) and energy was further studied, the result is consistent with the experimental result.

Low volumetric-energy-density caused by low tap density of nanomaterial seriously restricts the application of nanomaterial in lithium-ion batteries. Here, to solve this problem, micron-sized Fe2O3 secondary particles (MFSPs) with high tap density (2.8 g cm−3) are synthesized via a facile way. As a result, ultrahigh volumetric-energy-density of 1490 mA h cm−3 is obtained after 100 cycles at C/2 (∼500 mA g−1). Densely packed structure of MFSPs exhibits well structural stability and electrical conductivity. For the high areal mass loading of 4.02 mg cm−2, an areal capacity about 3 mA h cm−2 is achieved.

Lithium–sulfur batteries hold great promise for serving as next generation high energy density batteries. However, the shuttle of polysulfide induces rapid poor cycling stability of lithium–sulfur cells. Using an interlayer inserted between the sulfur cathode and the separator to capture these soluble intermediates can diminish this effect effectively. Herein, a ultrathin TiO2 nanotubes/graphene oxide (TiO2 NTs/GO) hybrid membrane (the thickness is less than 10 μm) used as an interlayer in lithium sulfur battery can effectively improve the cycle performance by trapping the soluble polysulfides. As a result, the sulfur cathode with TiO2 NTs/GO hybrid membrane as interlayer exhibits an initial discharge capacity of 1431.5 mA h g−1 and maintains the reversible capacity of 845.8 mA h g−1 at 0.1C after 100 cycles.

Tin dioxide (SnO2) is a promising anode material for lithium-ion batteries owing to its large theoretical capacity (1494 mA h g−1). However, its practical application is hindered by these problems: the low conductivity, which restricts rate performance of the electrode, and the drastic volume change (400%). In this study, we designed a novel polyacrylamide/SnO2 nanocrystals/graphene gel (PAAm@SnO2NC@GG) structure, in which SnO2 nanocrystals anchored in three-dimensional graphene gel network and the polyacrylamide layers could effectively prevent the agglomeration of SnO2 nanocrystals, presenting excellent cyclability and rate performance. A capacity retention of over 90% after 300 cycles of 376 mA h g−1 was achieved at a current density of 5 A g−1. In addition, a stable capacity of about 989 mA h g−1 at lower current density of 0.2 A g−1 was achieved.

Device and process of oxidization, degassing, acidity adjustment of 1BP (The Pu production feed from U/Pu separation section) from APOR process (Advanced Purex Process based on Organic Reductants) were improved through rational design and experiments. The device was simplified and the process parameters, such as feed position and flow ratio, were determined by experiments. Based on this new device and process, the reductants N , N -dimethylhydroxylamine (DMHAN) and methylhydrazine (MMH) in 1BP solution could be oxidized with much less N 2 O 4 consumption.

Tuning the free energy difference between a molecular probe and the target has been regarded as a feasible way to realize selective mutant recognition. But due to limited extent of variation on the probing sequences, it remains a challenge to moderately leverage the thermodynamic kinetics simply by changing the base composition of probes. Herein we propose the modulation of discrimination capability for single nucleotide variations (SNVs) detection by insertion of bulge-loop into duplex DNA probes. Based on controllable tuning of free energy change (ΔG) before and after strand exchange with either mutated or wild-type DNAs, much higher specificity than conventional linear probes is obtained. As-proposed bulge-loop probes allows excellent discrimination of SNVs in high guanine and cytosine (GC) rich regions, and reaches a detection limit of 0.02% abundance with down to 2 femtomolar target gene. The probes also demonstrate excellent consistence with droplet digital PCR (ddPCR) in identifying low abundant L858R mutant in lung tissue samples that are not resolved by either a commercial PCR kit or Sanger sequencing. Our work not only provides insight into the rational design of strand exchange probes for point-of-care diagnosis but also advance the construction of customizable cascade reactions in dynamic DNA nanotechnology more broadly.

The kinetics of reductive stripping of Np(VI) by Acetohydroxamic Acid from 30%TBP/kerosene was investigated using a high-speed stirred cell designed by ourselves. The phase separator for sampling was simple and powerful. The interfacial areas of different stirring speeds were determined by microphotograph method at 21 ℃ before the experiments. The effects of the different parameters as well as temperature were investigated systemically. The results showed that, at 21 ℃ the rate equation is − d[Np(VI)]/dt = k(S/V)[Np(VI)]0.78[AHA]0.46[HNO3]−0.20 − k′(S/V)[Np(V)]2.87, where k = (8.7 ± 0.7) × 10−7 (mol/L) –0.04m s –1, k′ = 1.1 ± 0.2 (mol/L) –2.87 m s –1, as c[HNO3] t = k(S/V)[Np(VI)]0.78[AHA]0.46[HNO3]−1.42 − k′(S/V)[Np(V)]2.87, where k = (3.2 ± 0.3) × 10−7 (mol/L)1.18 m s –1, k′ = 1.1 ± 0.2(mol/L) –2.87 m s –1 as c[HNO3] >= 1.0 mol/L, and S is the interfacial area, V the organic phase volume. The reductive stripping process is controlled by chemical reactions (kinetics regime) taking place at the interface. The apparent activation energy is 13.5 ± 0.2 kJ/mol.

To develop an aqueous reprocessing process for spent fuel of fast reactor, a counter current experiment (U-Pu co-stripping) based on a simplified PUREX process was carried out with 30%TBP/Kerosene solution containing U, Pu and HNO3. The experiment was done in a 16-stage miniature centrifugal contactor. The stripping percentage of U was 99.99%, Pu 99.94%. U stripping mainly took place in X1-feeding stage (11.00 mol/L HNO3 feeding stage) to the 16th one, while Pu stripping mainly took place in the first stage to the X1-feeding stage. And a simple method was presented to calculate c U/X1−feeding stage, Org when the X1-feeding stage number is more than 7 and the stripping percentage of U from the X1-feeding stage is more than 99.9% through the rear stages' stripping. The calculation results by this method were validated by Computer Simulation when only changing U concentrations in feed solution from 40.0 g/L to 90.0 g/L or only changing the X1-feeding stage from the 7th stage to the 11th one. Finally the optimized technology was given.

Summary The design of a new type of electroreduction mixer-settler for the partitioning of uranium and plutonium during the Purex process, which is featured with E-shaped cathodes and U-shaped anodes in settling chamber, is described and the operational results achieved using this equipment are presented. The results show that this new type of mixer-settler has excellent separation performances. The flow rate of organic feed solution is 3 mL/min and the flow ratio of feed solution (1BF) to aqueous back extraction stream (1BX) and to organic wash stream (1BS) is 4/1/1. For an organic feed of 84 g/L uranium and 1.40 ⁓ 2.64 g/L plutonium, both the separation factor of plutonium from uranium and that of uranium from plutonium are apparently higher than 104

Electrochemical reduction of uranyl nitrate is a green, simple way to make uranous ion. In order to improve the ratio of uranous ion to the total uranium and maintain high current efficiency, an electrolyser with very thin cathodic and anodic compartment, which were separated by a cation exchange membrane, was setup, and its performance was tested. The effects of various parameters on the reduction were also evaluated. The results show that the apparatus is quite positive. It runs well with 120 mA/cm2 current density (72 cm2 cathode, constant current batch operation). U(IV) yield can achieve 93.1 % (500 mL feed, total uranium 199 g/L) after 180 min electrolysis. It was also shown that when U(IV) yield was below 80 %, very high current efficiency was maintained, and there was almost a linear relationship between uranous ion yield and electrolysis time; under the range of experimental conditions, the concentration of uranyl nitrate, hydrazine, and nitric acid had little effect on the reduction.

Based on Eley-Rideal kinetic mechanism, one dimensional mathematical model for selective catalytic reduction reaction was established, in order to simulate the SCR process in the catalyst channel. The thermal effect on the reaction and the side effect of ammonia oxidation in the channel were considered simultaneously in the modeling. The model was testified to be reliable by compared with the experimental data. By the model, the concentration and temperature distributions in the channel were simulated. The effects of catalyst structure parameters, such as the pitch, the shape of catalyst channel and the monolithic catalyst type, on de-NOX efficiency were studied emphatically. The simulation results would be as an important reference for the design of SCR catalyst in the practical application.

Microwave-enhanced Fenton process (MEFP) is proposed as a new treatment for wastewater containing dimethyl sulfoxide (DMSO), which is difficult to treat using biological processes. Effects of microwave power, irradiation time, initial pH, hydrogen peroxide (H2O2) dosage, H2O2/Fe2+ molar ratio, and initial DMSO concentration were investigated to maximize DMSO removal in batch experiments. Further, a circulating-flow system for practical utility was devised and optimized via orthogonal experiments, and kinetic experiments were conducted to study the differences between MEFP and conventional heating-assisted Fenton process. Degradation and mineralization (conversion to CO2 and H2O) of DMSO were evaluated following degradation intermediates and total organic carbon (TOC). In MEFP, 95.8% DMSO removal was achieved within 5 min with a wide pH range (2–7). MEFP could achieve a much higher mineralization level (TOC removal of 51.3%) within much shorter time (10 min) than Fenton process stirring at ambient...

The kinetics of back-extraction of Pu(IV) from 30% Tri-Butyl-Phosphate/Odourless Kerosene (TBP/OK) into a nitric acid solution containing N,N-dimethylhydroxylamine (DMHAN) have been investigated using a Lewis cell. The different parameters affecting the back-extraction rate of Pu(IV) such as plutonium, nitric acid, DMHAN concentration in addition to temperature, stirring speed were separately studied and a rate equation was deduced. The activation energy of this process is 28.4 kJ/mol.

Kinetic studies of stripping of Np(IV) from 30% Tri-Butyl-Phosphate/Odourless Kerosene (TBP/OK) into a nitric acid solution containing acetohydroxamic acid (CH3CONHOH) have been investigated using a Lewis cell. The different parameters affecting the back-extraction rate of Np(IV) such as Np, TBP, nitric acid, nitrate, acetohydroxamic acid(AHA) concentration in addition to temperature, stirring speed and special interfacial area were separately studied and a rate equation was deduced. Results have been compared among themselves and other published works on similar systems. Mechanisms of stripping processes have been proposed.

The kinetics of the reductive stripping of plutonium(IV) by dihydroxyurea (DHU) in 30% TBP/kerosene-HNO3 system was studied with a constant interfacial area cell. The stripping rate of plutonium(IV) increases with the increase of the stirring speed of two phases and the interfacial area. The activation energy of this process is 28.4 kJ/mol. Under the given experimental conditions, the mass transfer of Pu is not controlled by redox reaction, but controlled by molecular diffusion from the organic phase to organic film layer and from the aqueous film layer to aqueous phase. The rate equation of reductive stripping (process is controlled by diffusion) was obtained as: r 0 = k′[Pu(IV)]0[DHU]a 0.16[HNO3]a −0.34. The rate constant k′ is (5.0±0.4)·10−2 (mol/L)0.18·min−1 at 18.0°C.

Electronic density functional calculations were used to explain the proposed formation of α-pyridyl from pyridine on silver, copper, cadmium, and gold surfaces. Our results show that the formation of α-pyridyl is governed by the mixing of metal wavefunctions with pyridine's near-HOMOs. When the organic orbitals mix with metal sp-character, a bonding interaction results and pyridine is the dominant surface species. If the metal orbitals mixing most strongly with the pyridine near-HOMOs are of d-character then an antibonding or nonbonding interaction results and α-pyridyl is the dominant surface species. A predicted correlation between the ratio of the concentration of the two surfaces species and the applied electrode potential is supported by analysis of surface-enhanced Raman data.

A surface enhanced Raman spectroscopy (SERS) investigation of the aggregation of silver nanoparticles formed via LVCC with diameters in the range 5–50 nm were studied. It was found that with 647.1 nm excitation maximum enhancement is observed using particles with 11 nm diameters. Upon addition of sodium halides, enhancement is proportional to the polarizability of the anion. Maximum enhancement was observed when the concentration of the anion is approximately equal to the concentration of the adsorbate.

The R-line luminescence is observed in the Raman spectra of α- and γ-Al2O3 with chromium concentrations of less than 1 ppm. The same signals were previously used to monitor the setting reaction of dental cements. With laser excitation 2O3. It is found that the intensities of R-line signals are related to the degree of hydration of the α-Al2O3 sample, which can be explained by the formation of additional octahedral sites for Cr3+ near the sample surface involving oxygen atoms from the Al2O3 matrix and from absorbed water molecules.