Decentralized Policy-Hidden Fine-Grained Redaction in Blockchain-Based IoT Systems.

Currently, decentralized redactable blockchains have been widely applied in IoT systems for secure and controllable data management. Unfortunately, existing works ignore policy privacy (i.e., the content of users' redaction policies), causing severe privacy leakage threats to users since users' policies usually contain large amounts of private information (e.g., health conditions and geographical locations) and limiting the applications in IoT systems. To bridge this research gap, we propose PFRB, a policy-hidden fine-grained redactable blockchain in decentralized blockchain-based IoT systems. PFRB follows the decentralized settings and fine-grained chameleon hash-based redaction in existing redactable blockchains. In addition, PFRB hides users' policies during policy matching such that apart from successful policy matching, users' policy contents cannot be inferred and valid redactions cannot be executed. Some main technical challenges include determining how to hide policy contents and support policy matching. Inspired by Newton's interpolation formula-based secret sharing, PFRB converts policy contents into polynomial parameters and utilizes multi-authority attribute-based encryption to further hide these parameters. Theoretical analysis proves the correctness and security against the chosen-plaintext attack. Extensive experiments on the FISCO blockchain platform and IoT devices show that PFRB achieves competitive efficiency over current redactable blockchains.

Defect-enhanced performance of a 3D graphene anode in a lithium-ion battery.

Morphological defects were generated in an undoped 3D graphene structure via the involvement of a ZnO and Mg(OH)2 intermediate nanostructure layer placed between two layers of vapor-deposited graphene. Once the intermediate layer was etched, the 3D graphene lost support and shrank; during this process many morphological defects were formed. The electrochemical performance of the derived defective graphene utilized as the anode of a lithium (Li)-ion battery was significantly improved from ∼382 mAh g-1 to ∼2204 mAh g-1 at 0.5 A g-1 compared to normal 3D graphene. The derived defective graphene exhibited an initial capacity of 1009 mAh g-1 and retention of 83% at 4 A g-1 for 500 cycles, and ∼330 mAh g-1 at a high rate of 20 A g-1. Complicated defects such as wrinkles, pores, and particles formed during the etching of the intermediate layer, were considered to contribute to the improvement of the electrochemical performance.

Construction of Well-Defined Redox-Responsive CO2 -Based Polycarbonates: Combination of Immortal Copolymerization and Prereaction Approach.

Due to the axial group initiation in traditional (salen)CoX/quaternary ammonium catalyst system, it is difficult to construct single active center propagating polycarbonates for copolymerization of CO2 /epoxides. Here a redox-responsive poly(vinyl cyclohexene carbonate) (PVCHC) with detachable disulfide-bond backbone is synthesized in a controllable manner using (salen)CoTFA/[bis(triphenylphosphine)iminium, [PPN]TFA binary catalyst, where the axial group initiation is depressed by judiciously choosing 3,3'-dithiodipropionic acid as starter. While for those comonomers failing to obtain polycarbonate with unimodal gel permeation chromatography (GPC) curve, a versatile method is developed by combination of immortal copolymerization and prereaction approach, and functional aliphatic polycarbonates having well-defined architecture and narrow polydispersity can be prepared. The resulting PVCHC can be further functionalized with alkenes by versatile cross-metathesis reaction to tune the physicochemical properties. The combination of immortal polymerization and prereaction approach creates a powerful platform for controllable synthesis of functional CO2 -based polycarbonates.

One-Step Reforming of CO2 and CH4 into High-Value Liquid Chemicals and Fuels at Room Temperature by Plasma-Driven Catalysis.

The conversion of CO2 with CH4 into liquid fuels and chemicals in a single-step catalytic process that bypasses the production of syngas remains a challenge. In this study, liquid fuels and chemicals (e.g., acetic acid, methanol, ethanol, and formaldehyde) were synthesized in a one-step process from CO2 and CH4 at room temperature (30 °C) and atmospheric pressure for the first time by using a novel plasma reactor with a water electrode. The total selectivity to oxygenates was approximately 50-60 %, with acetic acid being the major component at 40.2 % selectivity, the highest value reported for acetic acid thus far. Interestingly, the direct plasma synthesis of acetic acid from CH4 and CO2 is an ideal reaction with 100 % atom economy, but it is almost impossible by thermal catalysis owing to the significant thermodynamic barrier. The combination of plasma and catalyst in this process shows great potential for manipulating the distribution of liquid chemical products in a given process.

A Novel Polyurethane-Based Polyion Complex Material with Tunable Selectivity against Interferents for Selective Dopamine Determination.

Polyion complex (PIC) materials have been widely used in biosensors due to their molecular selectivity. However, achieving both widely controllable molecular selectivity and long-term solution stability with traditional PIC materials has been challenging due to the different molecular structures of polycations (poly-C) and polyanions (poly-A). To address this issue, we propose a novel polyurethane (PU)-based PIC material in which the main chains of both poly-A and poly-C are composed of PU structures. In this study, we electrochemically detect dopamine (DA) as the analyte and L-ascorbic acid (AA) and uric acid (UA) as the interferents to evaluate the selective property of our material. The results show that AA and UA are significantly eliminated, while DA can be detected with a high sensitivity and selectivity. Moreover, we successfully tune the sensitivity and selectivity by changing the poly-A and poly-C ratios and adding nonionic polyurethane. These excellent results were employed in the development of a highly selective DA biosensor with a detection range from 500 nM to 100 µM and a 3.4 µM detection limit. Overall, our novel PIC-modified electrode has the potential to advance biosensing technologies for molecular detection.

Plastering Sponge with Nanocarbon-Containing Slurry to Construct Mechanically Robust Macroporous Monolithic Catalysts for Direct Dehydrogenation of Ethylbenzene.

Nanocarbons have shown great potential as a sustainable alternative to metal catalysts, but their powder form limits their industrial applications. The preparation of nanocarbon-based monolithic catalysts is a practical approach for overcoming the resulting pressure drop associated with their powder form. In our previous work, a ploycation-mediated approach was used to successfully prepare nanocarbon-containing monoliths. Unfortunately, because there are no macropores in the monolith, it needs to be crashed into millimeter-sized particles before application. Therefore, developing a facile method for preparing mechanically robust nanocarbon-based macroporous monolithic catalysts is vital but still challenging. Herein, evoked by swallows building their nests, we report an approach for successfully preparing a mechanically robust nanodiamond-based macroporous monolith catalyst by plastering melamine sponge (MS) with a slurry composed of nanodiamonds (NDs) and poly(imidazolium-methylene) chloride (PImM) followed by an annealing process. The macroporous monolith catalyst (ND/NCMS-NCPImM) containing NDs well dispersed in N-doped carbon is mechanically robust with enriched macroscopic pores. It exhibits outstanding catalysis toward ethylbenzene to styrene through a direct dehydrogenation reaction with a high styrene rate in a steady state (5.50 mmol g-1 h-1) and high styrene selectivity (99.5%). ND/NCMS-NCPImM shows much higher activity than powder ND by 1.9 fold. In addition, this work solves the significant problem of large pressure drop encountered with conventional powdered nanocarbon catalysts in the flow reactor. This work not only creates an excellent nanodiamond-based macroporous monolithic ethylbenzene direct dehydrogenation catalyst but also presents a promising avenue for preparing other macroporous monolithic catalysts for diverse transformations.

Integrated fast-mass transfer and high Ti-sites utilization into hybrid amphiphilic TS@PMO catalyst towards efficient solvent-free methyl oleate epoxidation.

For solvent-free catalytic oxidations, low efficiency resulted from poor mass transfer and insufficient utilization of active centers remains a tough problem. Herein, we demonstrate a novel hybrid core-shell catalyst (TS@PMO) with an amphiphilic shell and a Ti-surface-enriched mesoporous TiO2-SiO2 (TS) core to address this challenge. Such TS@PMO realizes its amphiphilicity via an ex situ formed periodic mesoporous organosilica (PMO) shell. Simultaneously, by a unique etching effect induced by organic precursor growth on [SiO4] tetrahedra in TS core, active Ti sites are facilely enriched in near-surface layer of core and extra mesoporous cavities are introduced for substrate reservation. When applied for solvent-free epoxidation of methyl oleate (MO) with H2O2, TS@PMO exhibits remarkably boosted catalytic activity (X = 90.2%) and epoxide selectivity (S = 70.2%), overwhelming the unmodified titanosilicate (X = 63.7%, S = 49.2%) and Ti-containing organosilica (X = 39.8%, S = 25.0%). Such result benefits from an evidently enhanced interphase mass transfer and sufficiently accessible active Ti sites in TS@PMO. On the one hand, amphiphilic PMO shell can efficiently collect hydrophobic substrate and H2O2, while abundant mesopores in the shell offer open-path for them to access active sites in the core; on the other hand, an increased framework Ti (IV) density and their surface-enrichment in TS core greatly improve the utilization of active Ti sites. This study effectively makes up for the deficiencies of slow mass transfer and insufficient utilization of conventional titanosilicates in biphasic reactions, which paves a new avenue to exploit other hybrid catalysts for high-efficiency solvent-free catalysis.

Pearl Powder-An Emerging Material for Biomedical Applications: A Review.

Pearl powder is a well-known traditional Chinese medicine for a variety of indications from beauty care to healthcare. While used for over a thousand years, there has yet to be an in-depth understanding and review in this area. The use of pearl powder is particularly growing in the biomedical area with various benefits reported due to the active ingredients within the pearl matrix itself. In this review, we focus on the emerging biomedical applications of pearl powder, touching on applications of pearl powder in wound healing, bone repairing, treatment of skin conditions, and other health indications.

Efficacy of Water-Soluble Pearl Powder Components Extracted by a CO2 Supercritical Extraction System in Promoting Wound Healing.

Pearl powder is a biologically active substance that is widely used in traditional medicine, skin repair and maintenance. The traditional industrial extraction processes of pearl powder are mainly based on water, acid or enzyme extraction methods, all of which have their own drawbacks. In this study, we propose a new extraction process for these active ingredients, specifically, water-soluble components of pearl powder extracted by a CO2 supercritical extraction system (SFE), followed by the extraction efficiency evaluation. A wound-healing activity was evaluated in vitro and in vivo. This demonstrated that the supercritical extraction technique showed high efficiency as measured by the total protein percentage. The extracts exhibited cell proliferation and migration-promoting activity, in addition to improving collagen formation and healing efficiency in vivo. In brief, this study proposes a novel extraction process for pearl powder, and the extracts were also explored for wound-healing bioactivity, demonstrating the potential in wound healing.

The Physics of ultrafast saturable absorption in graphene.

The ultrafast saturable absorption in graphene is experimentally and theoretically investigated in the femtosecond (fs) time regime. This phenomenon is well-modeled with valence band depletion, conduction band filling and ultrafast intraband carrier thermalization. The latter is dominated by intraband carrier-carrier scattering with a scattering time of 8 ( +/- 3) fs, which is far beyond the time resolution of other ultrafast techniques with hundred fs laser pulses. Our results strongly suggest that graphene is an excellent atomic layer saturable absorber.

Extraction of alumina from alumina rich coal gangue by a hydro-chemical process.

Vast quantities of gangue from coal mining and processing have accumulated over the years and caused significant economic and environmental problems in China. For high added-value utilization of alumina rich coal gangue (ARCG), a mild hydro-chemical process was investigated to extract alumina. The influences of NaOH concentration, mass ratio of alkali to gangue, reaction temperature and reaction time were systematically studied. An alumina extraction rate of 94.68% was achieved at the condition of NaOH concentration 47.5%, alkali to gangue ratio of 6, reaction temperature of 260°C and reaction time of 120 min. The obtained leaching residues were characterized through X-ray diffraction, scanning electron microscopy and energy-dispersive spectrometer. Research confirmed that kaolinite the main alumina-bearing phase of ARCG can be decomposed and transformed to Na8Al6Si6O24(OH)2(H2O)2 and Ca2Al2SiO6(OH)2 at relatively low temperature and short reaction time. Additionally, Na8Al6Si6O24(OH)2(H2O)2 and Ca2Al2SiO6(OH)2 are unstable and will transform to alumina-free phase NaCaHSiO4 under the optimal conditions, which is the major reason for high alumina extraction rates.

Artificially innervated self-healing foams as synthetic piezo-impedance sensor skins.

Human skin is a self-healing mechanosensory system that detects various mechanical contact forces efficiently through three-dimensional innervations. Here, we propose a biomimetic artificially innervated foam by embedding three-dimensional electrodes within a new low-modulus self-healing foam material. The foam material is synthesized from a one-step self-foaming process. By tuning the concentration of conductive metal particles in the foam at near-percolation, we demonstrate that it can operate as a piezo-impedance sensor in both piezoresistive and piezocapacitive sensing modes without the need for an encapsulation layer. The sensor is sensitive to an object's contact force directions as well as to human proximity. Moreover, the foam material self-heals autonomously with immediate function restoration despite mechanical damage. It further recovers from mechanical bifurcations with gentle heating (70 °C). We anticipate that this material will be useful as damage robust human-machine interfaces.

Engineered nonlinear photonic quasicrystals for multi-frequency terahertz manipulation.

The interactions between electromagnetic wave and photonic quasicrystals are investigated. A terahertz (THz) source with multi-frequency modes in an optical LiTaO(3) superlattice produced by quasiperiodic (Fibonacci) domain-inverted ferroelectric material is demonstrated experimentally. Using the canonical pump-probe experimental technique, THz radiations in both forward and backward propagations are in-situ detected simultaneously. Four pronounced THz frequencies at 1.18, 0.78, 0.59 and 0.37 THz in Fourier transform spectrum are observed. The physical properties of THz waves inside quasiperiodic superlattice are discussed.

The synthesis of hierarchical high-silica beta zeolites in NaF media.

An aerosol-assisted hydrothermal method has been applied to synthesizing hierarchical beta zeolites with SiO2/Al2O3 ratios ranging from 44 to 392 in NaF media. Two different morphologies, including nano-aggregates with interparticle mesopores and plate-like zeolites with intracrystalline mesopores, can be formed depending on the SiO2/Al2O3 ratios of the synthesis gels. A possible mechanism for the formation of the beta zeolites has been proposed. The obtained beta zeolites show hierarchical pores, good Al species distribution and less internal defect sites. Evaluation, by the cracking of 1,3,5-triisopropylbenzene (1,3,5-TIPB), is consistent with the acidic properties and the pore structure of beta zeolites with different ratios of SiO2/Al2O3.

Explaining the influence of the introduced base sites into alkali oxide modified CsX towards side-chain alkylation of toluene with methanol.

The effect of the introduced base sites in CsX with alkali oxide modification towards side-chain alkylation of toluene with methanol was systematically investigated in the present work. A series of alkali oxide modified CsX with a base properties (base strength and amount) gradient were prepared by impregnating CsX with alkali metal hydroxide. Here, CsX with different base strengths were selected as the parent zeolite, which is favorable to clarify the different types of base site in the modified CsX. The base properties of the samples were elucidated based on the CO2-TPD results as well as with characterization by XPS and FT-IR of adsorbed CO2. It was revealed that the base strength of the oxygen atoms with negative charge (O δ-) in the zeolite framework can be strengthened by the electron donating function of the alkali oxides in the supercage of CsX. Detailed analysis of the correlation between the reaction behaviors of side-chain alkylation reaction and the base properties of the indicated catalysts was carried out. It was found that the dehydrogenation of methanol to formaldehyde step was promoted by the increasing base properties of O δ- in the CsX framework and that was the main reason for the promotion of the whole side-chain alkylation reaction. However, it was also found that the stronger base properties of the alkali oxide modified CsX would enhance the formation of active hydrogen atoms, which aggravated the unwanted styrene conversion to ethylbenzene.

Mesoporous Titanium-Silicalite Zeolite Containing Organic Templates as a Bifunctional Catalyst for Cycloaddition of CO2 and Epoxides.

Mesoporous TS-1 (MTS-1) containing organic templates tetrapropylammonium hydroxide (TPAOH) and polydiallyldimethylammonium chloride is synthesized and treated with different concentrations of hydrochloric acid aqueous solution. The as-synthesized MTS-1 are characterized using X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy, transmission electron microscopy, UV-vis, 13C cross-polarization/magic angle spinning (CP/MAS) NMR, thermogravimetry analysis, CO2-temperature-programmed desorption (TPD), N2 adsorption-desorption, X-ray fluorescence, and elemental analysis. The results of 13C CP/MAS NMR show that the structures of organic templates are retained after acid washing treatment. Not required to be removed by calcination, the organic templates embedded in MTS-1 can take the role of basic sites and activate carbon dioxide (CO2), which is confirmed by FT-IR. Moreover, the amount of acid sites and basic sites in the samples before and after acid treatment is characterized by modified Hammett indicator method and CO2-TPD, respectively. The results show that both the acidity and the basicity in the material are improved after acid washing. Thus, the sample after acid treatment contains two active sites: basic sites stemming from organic species and acid sites coming from framework Ti, which is beneficial to be used as a bifunctional catalyst in the cycloaddition reaction of CO2 and epoxides. It is highly active in the cycloaddition reaction, in which the conversion of epichlorohydrin (ECH) could reach 97.8% and the selectivity of cyclic carbonate is 98.0% under 1.6 MPa at 393 K for 6 h when acetonitrile is used as a solvent. Moreover, the kinetics of the cycloaddition reaction are studied using ECH as a substrate by varying the reaction parameters. More importantly, the organic-inorganic hybrid catalyst is reusable and stable against leaching of organic species in the cycloaddition reaction.

Silicalite-1 zeolite acidification by zinc modification and its catalytic properties for isobutane conversion.

A series of Zn-modified Silicalite-1 (S-1) zeolites (Zn x /S-1) were prepared by the wetness-impregnation method and applied in the catalytic conversion of isobutane. The structure and location of Zn species in Zn x /S-1 were investigated using UV-Vis and N2 physical adsorption. The acidity and origin of the acid sites in Zn x /S-1 were studied by NH3-temperature programmed desorption and Fourier-transform infrared analysis. The catalytic performance of Zn x /S-1 for isobutane conversion was investigated in a fixed-bed microreactor. In the experiments, the acidity of S-1 zeolite was dramatically increased by modification with Zn, with both Lewis and Brønsted sites identified in Zn x /S-1. The relationship between Brønsted acid sites and Zn-OH groups on ZnO clusters of Zn x /S-1 was also revealed for the first time. Furthermore, Zn x /S-1 catalysts exhibited excellent catalytic performances in both isobutane dehydrogenation and butene isomerization reactions. A high selectivity of total butene products ranging from 84.6 to 97.2 was achieved on the catalysts with different Zn loadings. Moreover, the linear correlation between isobutane conversion and the acid amount (determined by NH3-TPD) confirmed that the weak-to-medium acid sites in Zn x /S-1 should play a key role in isobutane conversion.

Plasma-Triggered CH4/NH3 Coupling Reaction for Direct Synthesis of Liquid Nitrogen-Containing Organic Chemicals.

Nitrogen-containing organic chemicals such as amines, amides, nitriles, and hydrazones are crucial in chemical and medical industries. This paper reports a direct synthesis of N,N-dimethyl cyanamide [(CH3)2NCN] and amino acetonitrile (NH2CH2CN) through a methane/ammonia (CH4/NH3) coupling reaction triggered by dielectric barrier discharge plasma, with by-products of hydrazine, amines, and hydrazones. The influence of CH4/NH3 molar ratio, feedstock residence time, and specific energy input on the CH4/NH3 plasma coupling reaction has been investigated and discussed. Under the optimized conditions, the productivities of (CH3)2NCN and NH2CH2CN reached 0.46 and 0.82 g·L-1·h-1, respectively, with 8.83% CH4 conversion. In addition, through combining the optical emission spectra diagnosis and the reaction results, a possible CH4/NH3 plasma coupling reaction mechanism has been proposed. This paper provides a potential fine application of CH4 and NH3 in green synthesis of liquid nitrogen-containing organic chemicals, such as nitriles, amines, amides, and hydrazones.

Low-temperature thermal reduction of suspended graphene oxide film for electrical sensing of DNA-hybridization.

A reduced graphene oxide (RGO) based capacitive real time bio-sensor was presented. Suspended graphene oxide (GO) film was assembled electrophoretically between the source and drain electrodes of a transistor and then reduced by annealing in hydrogen/nitrogen forming gas to optimize the surface functional groups and conductivity. The resonance frequency of the transmission coefficient (S21) of the transistor was observed to shift with deoxyribonucleic acid (DNA)-hybridization, with a detecting limit of ~5nM. The advantages of the bio-sensing approach include low-noise frequency output, solution based real time detection and capable of on-chip integration.