Showing papers by "Shandong Normal University published in 2018"

Electrochemical Ammonia Synthesis via Nitrogen Reduction Reaction on a MoS2 Catalyst: Theoretical and Experimental Studies.

Abstract: The discovery of stable and noble-metal-free catalysts toward efficient electrochemical reduction of nitrogen (N2 ) to ammonia (NH3 ) is highly desired and significantly critical for the earth nitrogen cycle. Here, based on the theoretical predictions, MoS2 is first utilized to catalyze the N2 reduction reaction (NRR) under room temperature and atmospheric pressure. Electrochemical tests reveal that such catalyst achieves a high Faradaic efficiency (1.17%) and NH3 yield (8.08 × 10-11 mol s-1 cm-1 ) at -0.5 V versus reversible hydrogen electrode in 0.1 m Na2 SO4 . Even in acidic conditions, where strong hydrogen evolution reaction occurs, MoS2 is still active for the NRR. This work represents an important addition to the growing family of transition-metal-based catalysts with advanced performance in NRR.

High-performance artificial nitrogen fixation at ambient conditions using a metal-free electrocatalyst

Abstract: Conversion of naturally abundant nitrogen to ammonia is a key (bio)chemical process to sustain life and represents a major challenge in chemistry and biology. Electrochemical reduction is emerging as a sustainable strategy for artificial nitrogen fixation at ambient conditions by tackling the hydrogen- and energy-intensive operations of the Haber–Bosch process. However, it is severely challenged by nitrogen activation and requires efficient catalysts for the nitrogen reduction reaction. Here we report that a boron carbide nanosheet acts as a metal-free catalyst for high-performance electrochemical nitrogen-to-ammonia fixation at ambient conditions. The catalyst can achieve a high ammonia yield of 26.57 μg h–1 mg–1cat. and a fairly high Faradaic efficiency of 15.95% at –0.75 V versus reversible hydrogen electrode, placing it among the most active aqueous-based nitrogen reduction reaction electrocatalysts. Notably, it also shows high electrochemical stability and excellent selectivity. The catalytic mechanism is assessed using density functional theory calculations. Electrochemical reduction of nitrogen is a promising route to industrial-scale nitrogen fixation at ambient conditions, but is challenged by activation of inert nitrogen. Here the authors report a metal-free catalyst that selectively reduces nitrogen to ammonia with high efficiency and stability.

Boosted Electrocatalytic N2 Reduction to NH3 by Defect-Rich MoS2 Nanoflower

Abstract: The industrial artificial fixation of atmospheric N-2 to NH3 is carried out using the Haber-Bosch process that is not only energy-intensive but emits large amounts of greenhouse gas. Electrochemical reduction offers an environmentally benign and sustainable alternative for NH3 synthesis. Although Mo-dependent nitrogenases and molecular complexes effectively catalyze the N-2 fixation at ambient conditions, the development of a Mo-based nanocatalyst for highly performance electrochemical N-2 fixation still remains a key challenge. Here, greatly boosted electrocatalytic N-2 reduction to NH3 with excellent selectivity by defect-rich MoS2 nanoflowers is reported. In 0.1 m Na2SO4, this catalyst attains a high Faradic efficiency of 8.34% and a high NH3 yield of 29.28 mu g h(-1) mg(cat.)(-1) at (-)0.40 V versus reversible hydrogen electrode, much larger than those of defect-free counterpart (2.18% and 13.41 mu g h(-1) mg(cat.)(-1)), with strong electrochemical stability. Density functional theory calculations show that the potential determining step has a lower energy barrier (0.60 eV) for defect-rich catalyst than that of defect-free one (0.68 eV).

Small-Molecule Fluorescent Probes for Imaging and Detection of Reactive Oxygen, Nitrogen, and Sulfur Species in Biological Systems

Abstract: Intracellular redox homeostasis provides broad implications in physiological and pathological fields. The disruption of redox homeostasis is closely associated with some human diseases, such as cancer, neurodegenerative diseases, cardiovascular diseases, diabetes mellitus, and gastrointestinal diseases.1-6 Therefore, cells possess an elaborate regulation system to maintain their redox balance and the large or significant redox state changes can be buffered by the redox-active molecules.7,8 These molecules experience interreaction and interconversion to facilitate the dynamic balance of intracellular redox state, among which three types of representative molecules should be mentioned, including reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species (RSS).

Reactive oxygen species signaling and stomatal movement in plant responses to drought stress and pathogen attack

Abstract: Stomata, the pores formed by a pair of guard cells, are the main gateways for water transpiration and photosynthetic CO2 exchange, as well as pathogen invasion in land plants. Guard cell movement is regulated by a combination of environmental factors, including water status, light, CO2 levels and pathogen attack, as well as endogenous signals, such as abscisic acid and apoplastic reactive oxygen species (ROS). Under abiotic and biotic stress conditions, extracellular ROS are mainly produced by plasma membrane-localized NADPH oxidases, whereas intracellular ROS are produced in multiple organelles. These ROS form a sophisticated cellular signaling network, with the accumulation of apoplastic ROS an early hallmark of stomatal movement. Here, we review recent progress in understanding the molecular mechanisms of the ROS signaling network, primarily during drought stress and pathogen attack. We summarize the roles of apoplastic ROS in regulating stomatal movement, ABA and CO2 signaling, and immunity responses. Finally, we discuss ROS accumulation and communication between organelles and cells. This information provides a conceptual framework for understanding how ROS signaling is integrated with various signaling pathways during plant responses to abiotic and biotic stress stimuli.

Abiotic Stresses: General Defenses of Land Plants and Chances for Engineering Multistress Tolerance.

Abstract: Abiotic stresses, such as low or high temperature, deficient or excessive water, high salinity, heavy metals, and ultraviolet radiation, are hostile to plant growth and development, leading to great crop yield penalty worldwide. It is getting imperative to equip crops with multistress tolerance to relieve the pressure of environmental changes and to meet the demand of population growth, as different abiotic stresses usually arise together in the field. The feasibility is raised as land plants actually have established more generalized defenses against abiotic stresses, including the cuticle outside plants, together with unsaturated fatty acids, reactive species scavengers, molecular chaperones, and compatible solutes inside cells. In stress response, they are orchestrated by a complex regulatory network involving upstream signaling molecules including stress hormones, reactive oxygen species, gasotransmitters, polyamines, phytochromes, and calcium, as well as downstream gene regulation factors, particularly transcription factors. In this review, we aimed at presenting an overview of these defensive systems and the regulatory network, with an eye to their practical potential via genetic engineering and/or exogenous application.

A biomimetic nanoreactor for synergistic chemiexcited photodynamic therapy and starvation therapy against tumor metastasis.

Abstract: Photodynamic therapy (PDT) is ineffective against deeply seated metastatic tumors due to poor penetration of the excitation light. Herein, we developed a biomimetic nanoreactor (bio-NR) to achieve synergistic chemiexcited photodynamic-starvation therapy against tumor metastasis. Photosensitizers on the hollow mesoporous silica nanoparticles (HMSNs) are excited by chemical energy in situ of the deep metastatic tumor to generate singlet oxygen (1O2) for PDT, and glucose oxidase (GOx) catalyzes glucose into hydrogen peroxide (H2O2). Remarkably, this process not only blocks the nutrient supply for starvation therapy but also provides H2O2 to synergistically enhance PDT. Cancer cell membrane coating endows the nanoparticle with biological properties of homologous adhesion and immune escape. Thus, bio-NRs can effectively convert the glucose into 1O2 in metastatic tumors. The excellent therapeutic effects of bio-NRs in vitro and in vivo indicate their great potential for cancer metastasis therapy.

MoO3 nanosheets for efficient electrocatalytic N2 fixation to NH3

Abstract: The synthesis of NH3 heavily depends on the energy-intensive Haber–Bosch process with a large amount of greenhouse gas emission. Electrochemical reduction offers a carbon-neutral process to convert N2 to NH3 at ambient conditions, but requires efficient and stable catalysts for the N2 reduction reaction. Mo-dependent nitrogenases and synthetic molecular complexes have attracted increasing attention for N2 fixation; however, less attention has been paid to Mo-based nanocatalysts for electrochemical N2 conversion to NH3. Herein, we report that MoO3 nanosheets act as an efficient non-noble-metal catalyst for electrochemical N2 fixation to NH3 with excellent selectivity at room temperature and atmospheric pressure. In 0.1 M HCl, this catalyst exhibits remarkable NRR activity with an NH3 yield of 4.80 × 10−10 mol s−1 cm−2 (29.43 μg h−1 mgcat.−1) and a faradaic efficiency of 1.9%. Moreover, this catalyst also shows high electrochemical stability and durability. Density functional theory calculations reveal that the outermost Mo atoms serve as the active sites for effective N2 adsorption.

Aspect-Aware Latent Factor Model: Rating Prediction with Ratings and Reviews

Abstract: Although latent factor models (e.g., matrix factorization) achieve good accuracy in rating prediction, they suffer from several problems including cold-start, non-transparency, and suboptimal recommendation for local users or items. In this paper, we employ textual review information with ratings to tackle these limitations. Firstly, we apply a proposed aspect-aware topic model (ATM) on the review text to model user preferences and item features from different aspects, and estimate the aspect importance of a user towards an item. The aspect importance is then integrated into a novel aspect-aware latent factor model (ALFM), which learns user's and item's latent factors based on ratings. In particular, ALFM introduces a weighted matrix to associate those latent factors with the same set of aspects discovered by ATM, such that the latent factors could be used to estimate aspect ratings. Finally, the overall rating is computed via a linear combination of the aspect ratings, which are weighted by the corresponding aspect importance. To this end, our model could alleviate the data sparsity problem and gain good interpretability for recommendation. Besides, an aspect rating is weighted by an aspect importance, which is dependent on the targeted user's preferences and targeted item's features. Therefore, it is expected that the proposed method can model a user's preferences on an item more accurately for each user-item pair locally. Comprehensive experimental studies have been conducted on 19 datasets from Amazon and Yelp 2017 Challenge dataset. Results show that our method achieves significant improvement compared with strong baseline methods, especially for users with only few ratings. Moreover, our model could interpret the recommendation results in depth.

Applications and potential of genome editing in crop improvement

Abstract: Genome-editing tools provide advanced biotechnological techniques that enable the precise and efficient targeted modification of an organism’s genome. Genome-editing systems have been utilized in a wide variety of plant species to characterize gene functions and improve agricultural traits. We describe the current applications of genome editing in plants, focusing on its potential for crop improvement in terms of adaptation, resilience, and end-use. In addition, we review novel breakthroughs that are extending the potential of genome-edited crops and the possibilities of their commercialization. Future prospects for integrating this revolutionary technology with conventional and new-age crop breeding strategies are also discussed.

Enhanced Photodynamic Therapy by Reduced Levels of Intracellular Glutathione Obtained By Employing a Nano-MOF with CuII as the Active Center.

Abstract: In photodynamic therapy (PDT), the level of reactive oxygen species (ROS) produced in the cell directly determines the therapeutic effect. Improvement in ROS concentration can be realized by reducing the glutathione (GSH) level or increasing the amount of photosensitizer. However, excessive amounts photosensitizer may cause side effects. Therefore, the development of photosensitizers that reduce GSH levels through synergistically improving ROS concentration in order to strengthen the efficacy of PDT for tumor is important. We report a nano-metal-organic framework (CuII -metalated nano-MOF {CuL-[AlOH]2 }n (MOF-2, H6 L=mesotetrakis(4-carboxylphenyl)porphyrin)) based on CuII as the active center for PDT. This MOF-2 is readily taken up by breast cancer cells, and high levels of ROS are generated under light irradiation. Meanwhile, intracellular GSH is considerably decreased owing to absorption on MOF-2; this synergistically increases ROS concentration and accelerates apoptosis, thereby enhancing the effect of PDT. Notably, based on the direct adsorption of GSH, MOF-2 showed a comparable effect with the commercial antitumor drug camptothecin in a mouse breast cancer model. This work provides strong evidence for MOF-2 as a promising new PDT candidate and anticancer drug.

Secure Cloud-Based EHR System Using Attribute-Based Cryptosystem and Blockchain

Abstract: To achieve confidentiality, authentication, integrity of medical data, and support fine-grained access control, we propose a secure electronic health record (EHR) system based on attribute-based cryptosystem and blockchain technology. In our system, we use attribute-based encryption (ABE) and identity-based encryption (IBE) to encrypt medical data, and use identity-based signature (IBS) to implement digital signatures. To achieve different functions of ABE, IBE and IBS in one cryptosystem, we introduce a new cryptographic primitive, called combined attribute-based/identity-based encryption and signature (C-AB/IB-ES). This greatly facilitates the management of the system, and does not need to introduce different cryptographic systems for different security requirements. In addition, we use blockchain techniques to ensure the integrity and traceability of medical data. Finally, we give a demonstrating application for medical insurance scene.

Oxygen vacancy derived local build-in electric field in mesoporous hollow Co3O4 microspheres promotes high-performance Li-ion batteries

Abstract: Urchin-like Co3O4 microspheres have been obtained through a two-step hydrothermal method followed by a post-calcination process and show a unique hollow structure with mesoporous nanosheets on their surface. Oxygen vacancies on the ultrathin nanosheets were introduced by annealing treatment, inducing a local built-in electric field to promote the migration of Li ions by Coulomb force during cycling and leading to a superior electrochemical performance for lithium-ion batteries. The electrodes containing urchin-like mesoporous hollow Co3O4 microspheres delivered a high discharge capacity of 2164.1 mA h g−1 at 0.05 A g−1 after 100 cycles. Even at a higher current density of 1.0 A g−1, a remarkable discharge capacity of 1307.9 mA h g−1 after 1000 cycles could still be achieved.

High-Performance Electrohydrogenation of N2 to NH3 Catalyzed by Multishelled Hollow Cr2O3 Microspheres under Ambient Conditions

Abstract: Electrohydrogenation of N2 to NH3 is emerging as an environmentally benign strategy to tackle the issues associated with the energy-intensive, CO2-emitting Haber–Bosch process. However, the method is severely challenged by N2 activation and needs efficient N2 reduction reaction (NRR) catalysts. Here, we report that multishelled hollow Cr2O3 microspheres (MHCMs), which are synthesized by a facile synthetic route, can serve as efficient and selective non-noble metal electrocatalysts for NRR. In 0.1 M Na2SO4 solution, the MHCMs achieve a high Faradaic efficiency (6.78%) and a large NH3 yield (25.3 μg h–1 mgcat–1) at −0.9 V vs reversible hydrogen electrode. The MHCMs also exhibit high stability during the reaction. Density functional theory calculations suggest that NRR over MHCMs occurs via both distal associative and partially alternative routes.

Passively mode-locked Er-doped fiber laser based on SnS 2 nanosheets as a saturable absorber

Abstract: In this paper, tin disulfide (SnS2), a two-dimensional (2D) n-type direct bandgap layered metal dichalcogenide with a gap value of 2.24 eV, was employed as a saturable absorber. Its appearance and nonlinear saturable absorption characteristics were also investigated experimentally. SnS2-PVA (polyvinyl alcohol) film was successfully prepared and employed as a mode-locker for achieving a mode-locked Er-doped fiber laser with a pulse width of 623 fs at a pulse repetition rate of 29.33 MHz. The results prove that SnS2 nanosheets will have wide potential ultrafast photonic applications due to their suitable bandgap value and excellent nonlinear saturable absorption characteristics.

Ti3C2Tx (T = F, OH) MXene nanosheets: conductive 2D catalysts for ambient electrohydrogenation of N2 to NH3

Abstract: The Haber–Bosch process for industrial-scale NH3 production suffers from high energy consumption and serious CO2 emission. Electrochemical N2 reduction is an attractive carbon-neutral alternative for NH3 synthesis but is severely restricted due to N2 activation needing efficient electrocatalysts for the N2 reduction reaction (NRR) under ambient conditions. Here, we report that Ti3C2Tx (T = F, OH) MXene nanosheets act as high-performance 2D NRR electrocatalysts for ambient N2-to-NH3 conversion with excellent selectivity. In 0.1 M HCl, such catalysts achieve a large NH3 yield of 20.4 µg h−1 mgcat.−1 and a high faradic efficiency of 9.3% at −0.4 V vs. reversible hydrogen electrode, with high electrochemical and structural stability. Density functional theory calculations reveal that N2 chemisorbed on Ti3C2Tx experiences elongation/weakness of the NN triple bond facilitating its catalytic conversion to NH3 and the distal NRR mechanism is more favorable with the final reaction of *NH2 to NH3 as the rate-limiting step.

Enabling Effective Electrocatalytic N2 Conversion to NH3 by the TiO2 Nanosheets Array under Ambient Conditions

Abstract: NH3 serves as an attractive hydrogen storage medium and a renewable energy sector for a sustainable future. Electrochemical reduction is a feasible ambient reaction to convert N2 to NH3, while it needs efficient electrocatalysts for the N2 reduction reaction (NRR) to meet the challenge associated with N2 activation. In this Letter, we report on our recent experimental finding that the TiO2 nanosheets array on the Ti plate (TiO2/Ti) is effective for electrochemical N2 conversion to NH3 at ambient conditions. When tested in 0.1 M Na2SO4, such TiO2/Ti attains a high NH3 yield of 9.16 × 10-11 mol s-1·cm-2 with corresponding Faradaic efficiency of 2.50% at -0.7 V vs reversible hydrogen electrode, outperforming most reported aqueous-based NRR electrocatalysts. It also shows excellent selectivity for NH3 formation with high electrochemical stability. The superior NRR activity is due to the enhanced adsorption and activation of N2 by oxygen vacancies in situ generated during electrochemical tests.

High performance MnO@C microcages with a hierarchical structure and tunable carbon shell for efficient and durable lithium storage

Abstract: A MnO@C microcage with a multi-structure and tunable carbon shell was fabricated through a facile bio-inspired synthesis strategy for highly reversible Li storage. Micrometer-sized MnO unit aggregates were covered with a porous carbon shell outside with a thickness of about 0.2 μm, and a graphene-analogous carbon network inside the MnO@C microcages. The carbon shell could be tunable by a graphene-base shell. The unique double-carbon-coating structure of the MnO@C microcages enabled realizing the high Li-storage performance of the MnO particles with a micrometer size. The electrode containing the MnO@C microcages delivered a high reversible capacity of 1450.5 mA h g−1 after 270 cycles at a current density of 0.1 A g−1, good rate capability, and outstanding cycling stability with a retention capacity of 805 mA h g−1 after 2000 cycles at a high current density of 1 A g−1. Quantitative kinetic analysis indicated that around 40% of the charge storage came from the capacitive contribution of the microcage structure. It was found that the tunable graphene-base shell could enhance the Li-ion diffusion rate significantly, and enable a stable ultralong long life cycle performance and enhanced rate performance of the microcages.

SERS activated platform with three-dimensional hot spots and tunable nanometer gap

Abstract: Hot spots have been considered as a dominant role in surface enhancement Raman scattering (SERS). Its generation cannot be separated from the ultra-small nanogaps, which will tremendously contribute to the strong electromagnetic field. We propose a AgNPs/graphene@AuNPs system with three-dimensional hot spots and tunable nanometer gap by changing the layer of graphene with a simple and facile method. The excellent SERS behaviors of the proposed AgNPs/graphene@AuNPs substrate are demonstrated experimentally using rhodamine 6G (R6G) and crystal violet (CV) as probe molecules and theoretically using commercial COMSOL software. The excellent SERS behaviors can be attributed to the electromagnetic mechanism (EM) in all three dimensions introduced by the lateral nanogaps (AgNP-AgNP) and the vertical nanogaps (AgNP-AuNPs), and the chemical enhancement mechanism (CM) induced by the graphene film. For practical application, the prepared sensitive AgNPs/graphene@AuNPs SERS substrate was used to detect Malachite green (MG) in sea water, which provides a bran-new avenue for the detection of biological and chemical molecule.

Enhanced activity of visible-light photocatalytic H2 evolution of sulfur-doped g-C3N4 photocatalyst via nanoparticle metal Ni as cocatalyst

Abstract: Sulfur doped graphitic carbon nitride g-S-C3N4 (denoted as SCN) was successfully prepared, and the SCN was further combined with metal Ni to prepare the photocatalyst with high visible-light photocatalytic activity. The Ni/g-S-C3N4 (denoted as NiSCN) composite photocatalyst was obtained by photodeposition method. Metal Ni species with the particle size about 5 nm were effectively supported on the surface of SCN. The NiSCN photocatalyst with the optimal Ni loading amounts exhibited an excellent H2-production rate of 2021.3 μmol g−1 h−1 under the visible light (λ > 420 nm). In addition, some Ni atoms might be embedded in the lattice structure of SCN. According to the experimental and computational results, the good utilization of visible light was attributed to the S and Ni doping, which upshifted the VB potential and narrowed the band gap of the photocatalyst. The metal Ni loaded on SCN surface improved the electron transfer rate and charge separation efficiency of the photocatalyst. Then, the H+ in water obtained the electrons on metal Ni to form H2 via the H radical intermediate.

Nuclear-Targeted Photothermal Therapy Prevents Cancer Recurrence with Near-Infrared Triggered Copper Sulfide Nanoparticles

Abstract: Clinical cancer treatments nowadays still face the challenge of recurrence due to the residual cancer cells and minute lesions in surgeries or chemotherapies. To effectively address the problem, we introduce a strategy for constructing cancer cell nuclear-targeted copper sulfide nanoparticles (NPs) with a significant photothermal effect to completely kill residual cancer cells and prevent local cancer recurrence. The NPs could directly target the tumor cells and further enter the nucleus by the surface modification of RGD and TAT peptides. Under the irradiation of 980 nm near-infrared laser, the NPs rapidly increase the temperature of the nucleus, destroy the genetic substances, and ultimately lead to an exhaustive apoptosis of the cancer cells. In vivo experiments show that the designed NPs could effectively treat cancer and prevent the return of cancer with a single laser irradiation for 5 min. The photothermal therapy strategy with nuclear targeting for cancer therapy and anti-recurrence will provide m...