Development of a Single-Molecule Nanobalance Ratiometric Electrochemical DNA Biosensor Using a Triblock Poly-Adenine Probe.

The development of electrochemical DNA biosensors has been limited by their reliability and reproducibility due to many interfering factors such as electrode properties, DNA surface densities, and complex biological samples. In this work, we developed a nanobalance polyA hairpin probe (polyA-HP), which was effectively assembled onto the gold electrode surface through the affinity between the central polyA fragment and the Au surface. One flanking probe of the polyA-HP captured the target sequence together with a MB-labeled signal probe, and the other flanking probe captured a reference probe simultaneously. The MB signal related to the amount of target was normalized by the reference Fc signal; thus, the signal-to-noise (S/N) was as high as 2000, and the reproducibility was remarkably improved to 2.77%, even facing deliberately changed experiment conditions. By designing a hairpin structure at the terminal of the polyA-HP, the selectivity and specificity were dramatically improved for the analysis of mismatched sequences. The analysis performance of biological samples was dramatically improved after normalization, which is critical for its practicability. Our novel biosensor is a universal single-molecule platform for ratiometric biosensors with excellent performance in real samples, indicating great potential for next-generation high-precision electrochemical sensors.

Fully Bio-Based Adhesive from Tannin and Sucrose for Plywood Manufacturing with High Performances.

Fully bio-based adhesives are beneficial to reduce the dependence of the wood adhesive industry on synthetic resins based on petrochemical resources and enhance the market competitiveness of adhesives. A fully bio-based wood adhesive composed of tannin and sucrose was developed and successfully used in the preparation of plywood. Effects of the preparation technology on the bonding strength and water resistance of plywood were investigated, and the properties of the adhesive were analyzed by Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG) and X-ray diffraction (XRD) in this study. The results showed that: (1) Compared with other biomass adhesives, tannin-sucrose adhesive had the characteristics of high-solid content and low viscosity, which had the potential to prepare particleboard and fiberboard. (2) A proper mass ratio of tannin to sucrose was key to obtaining a tannin-sucrose adhesive with better properties. (3) The optimum preparation process of tannin-sucrose adhesive for plywood was as follows: hot-pressing temperature of 210 °C, hot-pressing time of 1.2 min/mm, m(tannin):m(sucrose) of 60:40 and adhesive loading of 160 g/m2. Under these conditions, the water-resistant bonding strength of the plywood was 0.89 MPa, which met the strength requirements of the Type II standard of plywood in GB/T 17657-2013. (4) The hot-pressing temperature played a decisive role in the tannin-sucrose adhesive, and the good performance of the plywood was maintained when the temperature was 210 °C or above. Thus, the prepared tannin-sucrose adhesive had high-bonding strength, good water resistance and thermal stability.

Interfacial engineered RDX/TATB energetic co-particles for enhanced safety performance and thermal stability.

1,3,5-Trinitro-1,3,5-triazinane (RDX) has attracted considerable attention in energy-related fields. However, the safety performance of RDX needs to be improved in terms of various external stimuli. Herein, such issues of RDX could be well balanced through hydrothermal assembly with the assistance of insensitive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) in a low content of 10 wt% (named RT co-particles). The TATB spread outside and were embedded inside of the resultant RT co-particles, which were examined via X-ray computed tomography and a three-dimensional laser scanning confocal microscope. As a result, the impact safety performance of RT co-particles could be drastically enhanced to 17.5 J by the TATB lubricant effect, demonstrating over twice the value of that of raw RDX (6 J) and mixtures (7 J). Moreover, an interfacial reconstruction between RDX and TATB was witnessed due to the strong interfacial interaction, as examined by theoretical simulation. Inspired by this, a delayed exothermic decomposition temperature of RT co-particles (244.4 °C) has been achieved when compared with that of RDX (241.4 °C). As demonstrated, an energetic co-particle strategy may provide an effective pathway toward remarkably improved mechanical and thermal safety performance, shedding light on other energetic materials.

Triblock probe-polyA-probe electrochemical interfacial engineering for the sensitive analysis of RNAi plants.

RNA interference (RNAi) is currently under fast development, which brings improved crop quality and new activity against pests in agriculture, by producing RNAs to specifically inhibit gene expression. This technology, in turn, creates a pressing need for sensitive and specific analytical methods of exogenous RNA molecules in genetically modified (GM) crops for safety assessment and regulation of RNAi plants and their products. In this work, we developed a novel RNA electrochemical biosensor for the analysis of GM maize samples based on a polyA-DNA capturing probe containing three DNA segments: the central polyA segment combined onto a gold electrode surface with adjustable configuration and density, and two flanking DNA probes simultaneously captured the RNA targets through hybridization. Both the assembling and hybridization capability of our probe were demonstrated, and we systematically optimized the analytical conditions. Finally, the ultrasensitive detection of 10 fM RNA was realized without any amplification processes, and the specificity was verified by analyzing non-target maize samples. Our electrochemical biosensor provided a reliable and convenient measurement strategy for RNAi safety and quality assessment, and more importantly, our PAP (probe-polyA-probe) capturing probe exhibited an innovative design for the detection of large RNA molecules with complex secondary structures.

Porous MoS2 nanosheets for the fast decomposition of energetic compounds.

The energy release performance of energetic compounds like 3-nitro-1,2,4-trizole-5-one (NTO) and 5,5'-bistetrazole-1,1'-diolate (TKX-50) are indispensable in propellent formulations. However, thermal decomposition behavior is impeded by unfavorable catalysts. Presently, ultrathin porous MoS2 nanosheets (pMoS2) are considered as high-performance catalysts for NTO and TKX-50 decomposition. The pMoS2 in 5 wt% content could decrease the decomposition temperature of NTO and TKX-50 by 13.5 °C and 37.1 °C, respectively. Furthermore, the exothermic heat-release for pMoS2@NTO and pMoS2@TKX-50 were increased almost by a factor of two. The porous structure combined with large specific area of pMoS2 could mostly trigger the catalytic effect towards energetic compound decomposition. Additionally, the as-obtained MoS2 endowed advances in safety performance of NTO and TKX-50, with remarkably reduced impact and friction sensitivity. The as-proposed strategy may stimulate a different perspective towards the fast decomposition of energetic materials in propellants.

Litchi-like Core-Shell HMX@HPW@PDA Microparticles for Polymer-Bonded Energetic Composites with Low Sensitivity and High Mechanical Properties.

The reduction of interfacial interaction and the deterioration of mechanical properties by the introduction of the paraffin wax is a long-standing problem. To address it, a novel litchi-like core-shell 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX)@paraffin wax@polydopamine (PDA) structure was constructed with a new high melting point paraffin wax (HPW, 101.9 °C) as the inner shell and the bioinspired strong adhesive PDA as the exterior shell. The evolution of element states on the surface of energetic microcapsules conducted by X-ray photoelectron spectroscopy indicated the successful introduction of paraffin wax and PDA to form the core@double shell structure. Compared with the core@double shell particles based on the conventional low melting point paraffin wax (69.8 °C), the HMX@HPW@PDA particles demonstrated a 117% increase of impact energy EBAM from 6 J to 13 J by the Bundesanstalt für Materialprüfung (BAM) method. Attributed to the stronger interfacial interaction, the litchi-like core-shell HMX@paraffin wax@PDA-based energetic composites also exhibited much superior mechanical properties than that of the corresponding HMX@paraffin wax-based ones and could be equal to or even higher than that of the raw HMX-based ones. In addition, the ß-δ phase transition temperature of HMX in HMX@HPW@PDA crystals was improved by 11.3 °C than that of raw HMX. The simplicity and scalability of the described approach provided a creative opportunity for design and fabrication of energetic composites with high safety performance and mechanical properties.

Enhanced Interfacial and Mechanical Properties of PBX Composites via Surface Modification on Energetic Crystals.

The mechanical properties of composites are highly dependent on the interfacial interaction. In the present work, inspired by marine mussel, the adhesion between energetic crystals of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) and polymer binders was improved. Three types of linear polymeric agents of glycidyl azide polymer (GAP), polyethylene glycol (PEG), and polytetramethylene ether glycol (PTMEG) were grafted onto TATB particles bridged through polydopamine (PDA) films. SEM images showed that 5% grafting contents could evidently form roughness shells on the surface. With a reinforcement at the interface produced by grafting shells, the mechanical properties of polymer-bonded explosives (PBXs) exhibited outstanding mechanical performance, especially for the PTMEG-grafting sample. Examined by the contact-angle test, the PTMEG-grafting sample possessed a value of polar component similar to that of fluoropolymer, leading to an excellent wettability of the two phases. Additionally, different contents of PTMEG were grafted to reveal that the mechanical properties could be improved even with content as little as 0.5 wt.% PTMEG. These results might highlight a correlation between interfacial interaction and macroscopic properties for mechanically energetic composites, while providing a versatile route of grafting on highly loaded composites.

Core@Double-Shell Structured Energetic Composites with Reduced Sensitivity and Enhanced Mechanical Properties.

A novel core@double-shell (CDS) 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) based energetic composite was constructed with an inner nano-1,3,5-triamino-2,4,6-trinitrobenzene (nano-TATB) shell and outer polydopamine (PDA) shell fabricated via a facile ultrasonic method and a simple immersion method, respectively. The inner nano-TATB shell was chosen to reduce the sensitivity of HMX while maintaining explosion performance; the outer PDA shell was adopted to enhance the interfacial interaction between explosive crystals and polymer binder. The uniform PDA coating resulted in the increased ß-δ phase transition temperature of HMX from 197.0 to 212.8 °C. Because of the perfect and compact nano-TATB coating on the surface of the HMX particles, the impact sensitivity  was significantly decreased for the HMX@TATB@PDA particles (10 J), in comparison with the physical mixture with an equivalent composition (5 J). Polymer-bonded explosives (PBXs) based on CDS structured particles were designed and characterized in comparison with their core@single-shell (CSS) counterparts or physical mixtures. Due to the strong chemical and physical interfacial interaction, PBXs based on CDS structured particles displayed improved mechanical strength and roughness, storage modulus, as well as creep resistance.

Core-Shell Structured HMX@Polydopamine Energetic Microspheres: Synergistically Enhanced Mechanical, Thermal, and Safety Performances.

The solid⁻solid phase transition, poor mechanical properties, and high sensitivity has impeded further practical applications of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) based polymer bonded explosives (PBXs). To address these issues together, a facile and effective route was employed to achieve a coating of polydopamine (PDA) on the surface of explosive crystals via in situ polymerization of dopamine. Additionally, PBXs based on HMX@PDA microcapsules were prepared with a fluoropolymer as polymer binder. Improved storage modulus, static mechanical strength and toughness, and creep resistance has been achieved in as-prepared PDA modified PBXs. The ß-δ phase transition temperature of as-obtained PBXs based on conventional HMX (C-HMX)@PDA was improved by 16.3 °C. The friction sensitivity of the C-HMX based PBXs showed a dramatic drop after the PDA coating. A favorable balance proposed in this paper among thermal stability, mechanical properties, and sensitivity was achieved for C-HMX based PBXs with the incorporation of PDA.

Tuning the Reactivity of Metastable Intermixed Composite n-Al/PTFE by Polydopamine Interfacial Control.

The metastable intermixed composite (MIC) is one of the most popular research topics in the field of energetic materials (EMs). The goal is to invent EMs with tunable reactivity and desired energy content. However, it is very difficult to tune the reactivity of MIC due to its high reactivity and sensitivity caused by enlarged specific surface area and intimate contact between the oxidizers and fuels. Herein, we demonstrated a facile fabrication method that can be used to control the reactivity between the nanoaluminum (n-Al) and poly(tetrafluoroethylene) (PTFE) using an in situ-synthesized polydopamine (PDA) binding layer. It was found that PDA can adhere to both n-Al and PTFE particles, resulting in integrated n-Al@PDA/PTFE MICs. In comparison with traditional n-Al/PTFE MICs, the n-Al@PDA/PTFE showed an increased energy release and reduced sensitivity and more importantly tunable reactivity. By regulating the experimental conditions of coating, the thickness of PDA could be well controlled, which makes the tunable reactivity of n-Al@PDA/PTFE possible. The PDA interfacial layer may increase the preignition reaction (PIR) heat of Al2O3/PTFE and therefore the overall reaction heat of n-Al/PTFE. It also reveals that the PDA interfacial layer postponed the PIR, leading to an increase in onset thermal decomposition temperature ( To). As To increased, a more complete reaction between PTFE and Al nanoparticles could be achieved.

Production of light olefins by catalytic conversion of lignocellulosic biomass with HZSM-5 zeolite impregnated with 6wt.% lanthanum.

Catalytic conversion of rice husk, sawdust, sugarcane bagasse, cellulose, hemicellulose and lignin into olefins was performed with HZSM-5 containing 6 wt.% lanthanum. The olefins yields for different feedstocks decreased in the order: cellulose>hemicellulose>sugarcane bagasse>rice husk>sawdust>lignin. Biomass containing higher content of cellulose or hemicellulose produced more olefins than feedstocks with higher content of lignin. Among the biomass types, sugarcane bagasse provided the highest olefin yield of 0.12 kg olefins/(kg dry biomass) and carbon yield of 21.2C-mol%. Temperature, residence time and the catalyst/feed ratio influenced olefin yield and selectivity. While the HZSM-5 zeolite was catalytically active, the incorporation of lanthanum at 2.9, and 6.0 wt.% increased the production of olefins from rice husk by 15.6% and 26.5%, respectively. The conversion of biomass to light olefins potentially provides an alternative and sustainable route for production of the key petrochemicals.

Selective conversion of bio-oil to light olefins: controlling catalytic cracking for maximum olefins.

Light olefins are the basic building blocks for the petrochemical industry. In this work, selective production of light olefins from catalytic cracking of bio-oil was performed by using the La/HZSM-5 catalyst. With a nearly complete conversion of bio-oil, the maximum yield reached 0.28±0.02 kg olefins/(kg bio-oil), which was close to that from methanol. Addition of La into zeolite efficiently changed the total acid amount of HZSM-5, especially the acid distribution among the strong, medium and weak acid sites. A moderate increase of the number of the medium acid sites effectively enhanced the olefins selectivity and improved the catalyst stability. The comparison between the catalytic cracking and pyrolysis of bio-oil was studied. The mechanism of the conversion of bio-oil to light olefins was also discussed.

High efficient conversion of CO2-rich bio-syngas to CO-rich bio-syngas using biomass char: a useful approach for production of bio-methanol from bio-oil.

A novel approach for high efficient conversion of the CO(2)-rich bio-syngas into the CO-rich bio-syngas was carried out by using biomass char and Ni/Al(2)O(3) catalyst, which was successfully applied for production of bio-methanol from bio-oil. After the bio-syngas conditioning, the CO(2)/CO ratio prominently dropped from 6.33 to 0.01-0.28. The maximum CO yield in the bio-syngas conditioning process reached about 1.96 mol/(mol CO(2)) with a nearly complete conversion of CO(2) (99.5%). The performance of bio-methanol synthesis was significantly improved via the conditioned bio-syngas, giving a maximum methanol yield of 1.32 kg/(kg(catalyst)h) with a methanol selectivity of 99%. Main reaction paths involved in the bio-syngas conditioning process have been investigated in detail by using different model mixture gases and different carbon sources.