Bio-catalytic nanoparticle shaping for preparing mesoscopic assemblies of semiconductor quantum dots and organic molecules.

We report a unique bio-catalytic nanoparticle shaping (BNS) method for preparing a variety of mesoscopic particles by a facile process. For example, the BNS method affords mesoscopic QD assembly dispersions. Large-size sedimentations (>1 µm) of QDs are first formed using oligo-L-lysine linkers. These then undergo controlled enzymatic cleavage of the linkers using trypsin, which surprisingly leads to mesoscopic particles about 84 nm in size with a narrow size distribution. A detailed mechanism of the BNS method is investigated using tetrakis(4-carboxyphenyl)porphyrin (TCPP), instead of QDs, as a probe molecule. Interestingly, the BNS method can also be applied to other combinations of enzymes and enzymatically degradable linkers, such as hyaluronidase with hyaluronan. As a potential application, the mesoscopic particles of QDs and oligo-lysine exhibit their ability to act as a drug delivery carrier originating from the features of both QDs and oligo-lysine. The BNS method demonstrates the universality and versatility of preparing mesoscopic particles and opens new doors for studying QD assemblies and molecular-based mesoscopic particles.

Recent Progress on Durable Metal-N-C Catalysts for Proton Exchange Membrane Fuel Cells.

It is essential for the widespread application of proton exchange membrane fuel cells (PEMFCs) to investigate low-cost, extremely active, and long-lasting oxygen reduction catalysts. Initial performance of PGM-free metal-nitrogen-carbon (M-N-C) catalysts for oxygen reduction reaction (ORR) has advanced significantly, particularly for Fe-N-C-based catalysts. However, the insufficient stability of M-N-C catalysts still impedes their use in practical fuel cells. In this review, we focus on the understanding of the structure-stability relationship of M-N-C ORR catalysts and summarize valuable guidance for the rational design of durable M-N-C catalysts. In the first section of this review, we discuss the inherent degrading mechanisms of M-N-C catalysts, such as carbon corrosion, demetallation, H2 O2 attack, etc. As we gain a thorough comprehension of these deterioration mechanisms, we shift our attention to the investigation of strategies that can mitigate catalyst deterioration and increase its stability. These strategies include enhancing the anti-oxidation of carbon, fortifying M-N bonds, and maximizing the effectiveness of free radical scavengers. This review offers a prospective view on the enhancement of the stability of non-noble metal catalysts.

Dynamic Behavior of Intermediate Adsorbates to Control Activity and Product Selectivity in Heterogeneous Catalysis: Methanol Decomposition on Pt/TiO2(110).

Dynamic behavior of intermediate adsorbates, such as diffusion, spillover, and reverse spillover, has a strong influence on the catalytic performance in oxide-supported metal catalysts. However, it is challenging to elucidate how the intermediate adsorbates move on the catalyst surface and find active sites to give the corresponding products. In this study, the effect of the dynamic behavior of methoxy intermediate on methanol decomposition on a Pt/TiO2(110) surface has been clarified by combination of scanning tunneling microscopy (STM), temperature-programmed desorption (TPD), and density functional theory (DFT) calculations. The methoxy intermediates were formed by the dissociative adsorption of methanol molecules on Pt nanoparticles at room temperature followed by spillover to the TiO2(110) support surface. TPD results showed that the methoxy intermediates were thermally decomposed at >350 K on the Pt sites to produce CO (dehydrogenation) and CH4 (C-O bond scission). A decrease of the Pt nanoparticle density lowered the activity for the decomposition reaction and increased the selectivity toward CH4, which indicates that the reaction is controlled by diffusion and reverse spillover of the methoxy intermediates. Time-lapse STM imaging and DFT calculations revealed that the methoxy intermediates migrate on the five-fold coordinated Ti (Ti5c) sites along the [001] or [11¯0] direction with the aid of hydrogen adatoms bonded to the bridging oxygens (Obr) and can move over the entire surface to seek and find active Pt sites. This work offers an in-depth understanding of the important role of intermediate adsorbate migration in the control of the catalytic performance in oxide-supported metal catalysts.

Monomicelle-Directed Engineering of Strained Carbon Nanoribbons as Oxygen Reduction Catalyst.

To date, precisely tailoring local active sites of well-defined earth-abundant metal-free carbon-based electrocatalysts for attractive electrocatalytic oxygen reduction reaction (ORR), remains challenging. Herein, the authors successfully introduce a strain effect on active C-C bonds adjacent to edged graphitic nitrogen (N), which raises appropriate spin-polarization and charge density of carbon active sites and kinetically favor the facilitation of O2 adsorption and the activation of O-containing intermediates. Thus, the constructed metal-free carbon nanoribbons (CNRs-C) with high-curved edges exhibit outstanding ORR activity with half-wave potentials of 0.78 and 0.9 V in 0.5 m H2 SO4 and 0.1 m KOH, respectively, overwhelming the planar one (0.52 and 0.81 V) and the N-doped carbon sheet (0.41 and 0.71 V). Especially in acidic media, the kinetic current density (Jk ) is 18 times higher than that of the planar one and the N-doped carbon sheet. Notably, these findings show the spin polarization of the asymmetric structure by introducing a strain effect on the C-C bonds for boosting ORR.

Highly Stable Pt-Based Oxygen Reduction Electrocatalysts toward Practical Fuel Cells: Progress and Perspectives.

The high cost and poor reliability of cathodic electrocatalysts for the oxygen reduction reaction (ORR), which requires significant amounts of expensive and scarce platinum, obstructs the broad applications of proton exchange membrane fuel cells (PEMFCs). The principles of ORR and the reasons for the poor stability of Pt-based catalysts are reviewed. Moreover, this paper discusses and categorizes the strategies for enhancing the stability of Pt-based catalysts in fuel cells. More importantly, it highlights the recent progress of Pt-based stability toward ORR, including surface-doping, intermetallic structures, 1D/2D structures, rational design of support, etc. Finally, for atomic-level in-depth information on ORR catalysts in fuel cells, potential perspectives are suggested, such as large-scale preparation, advanced interpretation techniques, and advanced simulation. This review aims to provide valuable insights into the fundamental science and technical engineering for practical Pt-based ORR electrocatalysts in fuel cells.

Cooperative Catalysis of Vibrationally Excited CO2 and Alloy Catalyst Breaks the Thermodynamic Equilibrium Limitation.

Using nonthermal plasma (NTP) to promote CO2 hydrogenation is one of the most promising approaches that overcome the limitations of conventional thermal catalysis. However, the catalytic surface reaction dynamics of NTP-activated species are still under debate. The NTP-activated CO2 hydrogenation was investigated in Pd2Ga/SiO2 alloy catalysts and compared to thermal conditions. Although both thermal and NTP conditions showed close to 100% CO selectivity, it is worth emphasizing that when activated by NTP, CO2 conversion not only improves more than 2-fold under thermal conditions but also breaks the thermodynamic equilibrium limitation. Mechanistic insights into NTP-activated species and alloy catalyst surface were investigated by using in situ transmission infrared spectroscopy, where catalyst surface species were identified during NTP irradiation. Moreover, in in situ X-ray absorption fine-structure analysis under reaction conditions, the catalyst under NTP conditions not only did not undergo restructuring affecting CO2 hydrogenation but also could clearly rule out catalyst activation by heating. In situ characterizations of the catalysts during CO2 hydrogenation depict that vibrationally excited CO2 significantly enhances the catalytic reaction. The agreement of approaches combining experimental studies and density functional theory (DFT) calculations substantiates that vibrationally excited CO2 reacts directly with hydrogen adsorbed on Pd sites while accelerating formate formation due to neighboring Ga sites. Moreover, DFT analysis deduces the key reaction pathway that the decomposition of monodentate formate is promoted by plasma-activated hydrogen species. This work enables the high designability of CO2 hydrogenation catalysts toward value-added chemicals based on the electrification of chemical processes via NTP.

Concave Pt-Zn Nanocubes with High-Index Faceted Pt Skin as Highly Efficient Oxygen Reduction Catalyst.

High dosage of expensive Pt to catalyze the sluggish oxygen reduction reaction (ORR) on the cathode severely impedes the commercialization of proton exchange membrane fuel cells. Therefore, it is urgent to cut down the Pt catalyst by efficiently improving the ORR activity while maintaining high durability. Herein, magic concave Pt-Zn nanocubes with high-index faceted Pt skin (Pt78 Zn22 ) are proposed for high-efficiency catalysis toward proton exchange membrane fuel cells. These unique structural features endow the Pt-skin Pt78 Zn22 /KB with a mass activity of 1.18 mA µgPt -1 and a specific activity of 3.64 mA cm-2 for the ORR at 0.9 V (vs RHE). Meanwhile, the H2 -O2 fuel cell assembled by this catalyst delivers an ultrahigh peak power density of ≈1449 mW cm-2 . Both experiments and theoretical calculations show that the electronic structure of the surface is adjusted, thereby shortening the length of the Pt-Pt bond and reducing the adsorption energy of OH*/O* on the Pt surface. This work demonstrates the synergistic effect of the oxidation-resistant metal Zn and the construction of Pt-rich surface engineering. Also, it guides the future development of catalysts for their practical applications in energy conversion technologies and beyond.

Evolution of Cu single atom catalysts to nanoclusters during CO2 reduction to CO.

We synthesized Cu single atoms embedded in a N-doped porous carbon catalyst with a high Faradaic efficiency of 93.5% at -0.50 V (vs. RHE) for CO2 reduction to CO. The evolution of Cu single-atom sites to nanoclusters of about 1 nm was observed after CO2 reduction at a potential lower than -0.30 V (vs. RHE). The DFT calculation indicates that Cu nanoclusters improve the CO2 activation and the adsorption of intermediate *COOH, thus exhibiting higher catalytic activity than CuNx sites. The structural instability observed in this study helps in understanding the actual active sites of Cu single atom catalysts for CO2 reduction.

Boosting Nitrogen Reduction to Ammonia on FeN4 Sites by Atomic Spin Regulation.

Understanding the relationship between the electronic state of active sites and N2 reduction reaction (NRR) performance is essential to explore efficient electrocatalysts. Herein, atomically dispersed Fe and Mo sites are designed and achieved in the form of well-defined FeN4 and MoN4 coordination in polyphthalocyanine (PPc) organic framework to investigate the influence of the spin state of FeN4 on NRR behavior. The neighboring MoN4 can regulate the spin state of Fe center in FeN4 from high-spin (dxy 2 dyz 1 dxz 1 d z 2 1 d x 2 - y 2 1 ) to medium-spin (dxy 2 dyz 2 dxz 1 d z 2 1 ), where the empty d orbitals and separate d electron favor the overlap of Fe 3d with the N 2p orbitals, more effectively activating N≡N triple bond. Theoretical modeling suggests that the NRR preferably takes place on FeN4 instead of MoN4 , and the transition of Fe spin state significantly lowers the energy barrier of the potential determining step, which is conducive to the first hydrogenation of N2 . As a result, FeMoPPc with medium-spin FeN4 exhibits 2.0 and 9.0 times higher Faradaic efficiency and 2.0 and 17.2 times higher NH3 yields for NRR than FePPc with high-spin FeN4 and MoPPc with MoN4 , respectively. These new insights may open up opportunities for exploiting efficient NRR electrocatalysts by atomically regulating the spin state of metal centers.

Regulating Fe-spin state by atomically dispersed Mn-N in Fe-N-C catalysts with high oxygen reduction activity.

As low-cost electrocatalysts for oxygen reduction reaction applied to fuel cells and metal-air batteries, atomic-dispersed transition metal-nitrogen-carbon materials are emerging, but the genuine mechanism thereof is still arguable. Herein, by rational design and synthesis of dual-metal atomically dispersed Fe,Mn/N-C catalyst as model object, we unravel that the O2 reduction preferentially takes place on FeIII in the FeN4 /C system with intermediate spin state which possesses one eg electron (t2g4eg1) readily penetrating the antibonding π-orbital of oxygen. Both magnetic measurements and theoretical calculation reveal that the adjacent atomically dispersed Mn-N moieties can effectively activate the FeIII sites by both spin-state transition and electronic modulation, rendering the excellent ORR performances of Fe,Mn/N-C in both alkaline and acidic media (halfwave positionals are 0.928 V in 0.1 M KOH, and 0.804 V in 0.1 M HClO4), and good durability, which outperforms and has almost the same activity of commercial Pt/C, respectively. In addition, it presents a superior power density of 160.8 mW cm-2 and long-term durability in reversible zinc-air batteries. The work brings new insight into the oxygen reduction reaction process on the metal-nitrogen-carbon active sites, undoubtedly leading the exploration towards high effective low-cost non-precious catalysts.

Interfacial Structure of Water as a New Descriptor of the Hydrogen Evolution Reaction.

Driven by the persisting poor understanding of the sluggish kinetics of the hydrogen evolution reaction (HER) on Pt in alkaline media, a direct correlation of the interfacial water structure and activity is still yet to be established. Herein, using Pt and Pt-Ni nanoparticles we first demonstrate a strong dependence of the proton donor structure on the HER activity and pH. The structure of the first layer changes from the proton acceptors to the donors with increasing pH. In the base, the reactivity of the interfacial water varied its structure, and the activation energies of water dissociation increased in the sequence: the dangling O-H bonds < the trihedrally coordinated water < the tetrahedrally coordinated water. Moreover, optimizing the adsorption of H and OH intermediates can re-orientate the interfacial water molecules with their H atoms pointing towards the electrode surface, thereby enhancing the kinetics of HER. Our results clarified the dynamic role of the water structure at the electrode-electrolyte interface during HER and the design of highly efficient HER catalysts.

Intracellular MicroRNA Imaging with MoS2-Supported Nonenzymatic Catassembly of DNA Hairpins.

Amplification strategies for low-level microRNA detection in living cells are pivotal for gene diagnosis and many cellular bioprocesses. In this work, we develop an amplification strategy for microRNA-21 (miRNA-21) imaging in living cells with MoS2-supported catassembly of DNA hairpins. The MoS2 nanosheet with low cytotoxicity serves as the nanocarrier and excellent fluorescence quencher, which can transfer fluorescent metastable hairpin DNA into the cells easily in a nondestructive manner and significantly reduce background signals. The three-branched catalyzed hairpin assembly (TB-CHA) probes contain three types of designed DNA molecular beacons with the modification of Cy3 in the terminal. In the presence of miRNA-21, the catalyzed hairpin assembly (CHA) reaction would be triggered and a "Y"-shaped three-branched duplex nanostructure would be formed, which would release from the surface of the MoS2 nanosheet due to the reduced affinity between the DNA duplex and MoS2 nanosheet. The multisite fluorescence modification and the circular reaction of TB-CHA probes allowed a significant fluorescence recovery in a live-cell microenvironment. The ultrasensitive detection of miRNA-21 is achieved with a detection limit of 75.6 aM, which is ∼5 orders of magnitude lower than that of a simple strand displacement-based strategy (detection limit: 8.5 pM). This method offers great opportunities for the ultrasensitive live-cell detection of miRNAs and helps in gaining a deeper understanding of the physiological functions of miRNAs in cancer research and life processes.

Cancer-Specific MicroRNA Analysis with a Nonenzymatic Nucleic Acid Circuit.

Sensitive detection of gastric cancer-related biomarkers in human serum provides a promising means for early cancer diagnosis. Herein, we report the design of a nucleic acid circuit for gastric cancer-related microRNA-27a (miRNA-27a) detection based on dual toehold-mediated circular strand displacement amplification (CSDA). In the presence of miRNA-27a, the hybridization between miRNA-27a and probe DNA on magnetic beads through toehold 1 leads to the release of fluorescent DNA and the exposure of a new toehold 2 on linker DNA. After hybridization with catalytic DNA, CSDA is initiated and target miRNA-27a is released to participate in the next cyclic reaction; therefore, a greatly enhanced fluorescence signal is produced. The efficient magnetic separation makes the sensitive detection of miRNA-27a be accomplished within 45 min. With the efficient CSDA, the detection limit of the system (0.8 pM) is ∼100 folds lower than that of the system based on strand displacement without CSDA (79.3 pM). Furthermore, the system also showed good stability and sensitivity to discriminate single-base mismatch, which allows the detection of miRNA-27a in human serum samples. This study provides a novel platform and approach for the rapid quantitative determination of miRNA, which has great potential in clinical diagnosis and disease treatment.

Cu overlayers on tetrahexahedral Pd nanocrystals with high-index facets for CO2 electroreduction to alcohols.

We investigated CO2 electroreduction on Cu overlayers on tetrahexahedral Pd nanocrystals with {310} high-index facets, which exhibited a high Faradaic efficiency towards alcohols. The selectivity to ethanol or methanol can be readily tuned by changing the Cu coverage.

Seeds and Potentials Mediated Synthesis of High-Index Faceted Gold Nanocrystals with Enhanced Electrocatalytic Activities.

Because high-index facets (HIFs) possess high surface energy, the metal nanoparticles enclosed with HIFs are eliminated during their growth in a conventional shape-controlled synthesis due to the thermodynamics that drives the particles minimizing their total surface energy. This study develops a double-step potential method to prepare an unprecedentedly stellated Au nanocrystals (NCs) bounded by high-index {711} and {331} facets in deep eutectic solvent (DES) medium. The formation of Au NCs bounded by HIFs was systematically studied. It has demonstrated that the shapes of Au NCs are strongly dependent on the size of seeds and the growth potentials as well as the urea adsorbates in the DES. By adjusting the size of seeds and the growth potentials, the stellated Au NCs can be transformed into concave hexoctahedra (HOH) with high-index {421} facets and concave trisoctahedra (TOH) with high-index {991} facets. The electrocatalytic activities of the as-prepared Au NCs are evaluated by glucose oxidation. Thanks to HIFs having high density of atomic steps and kinks, the stellated, TOH, and HOH Au NCs exhibit higher electrocatalytic activity than that of the polycrystalline Au electrode, demonstrating that the steps and kinks serve as the active sites and play an important role in glucose electro-oxidation.

LncRNA-MALAT1 Promotes Angiogenesis of Thyroid Cancer by Modulating Tumor-Associated Macrophage FGF2 Protein Secretion.

Tumor-associated macrophages (TAMs) in the tumor microenvironment have been associated with enhanced tumor progression. In this study, we investigated the role and molecular mechanisms of MALAT1 in TAMs derived from thyroid cancer. The expression of MALAT1 and FGF2 in thyroid cancer tissues and cells were measured by quantitative real-time PCR and Western blot. TAMs were transfected with indicated constructs. Then the culture medium (CM) from TAMs was harvested for assay. Secreted FGF2 protein levels and TNF-α, IL-12, and IL-10 levels were detected by ELISA. The cell proliferation, migration, and invasion of FTC133 cells were determined with a CCK-8 assay and a Transwell assay, respectively. In addition, HUVEC vasculature formation was measured by matrigel angiogenesis assay. The higher levels of MALAT-1 and FGF2 were observed in thyroid cancer tissues and in thyroid cancer cells compared to that in the control. Besides, in the presence of si-MALAT1, the levels of TNF-α and IL-12 were significantly up-regulated whereas IL-10 was down-regulated in the CM from TAMs. Moreover, down-regulation of MALAT1 in TAMs reduced proliferation, migration, and invasion of FTC133 cells and inhibited angiogenesis. However, overexpression of FGF2 blocked the effects of MALAT1 siRNAs on cell migration, invasion, and angiogenesis. Our results suggest that MALAT1-mediated FGF2 protein secretion from TAMs inhibits inflammatory cytokines release, promotes proliferation, migration, and invasion of FTC133 cells and induces vasculature formation. J. Cell. Biochem. 118: 4821-4830, 2017. © 2017 Wiley Periodicals, Inc.

Platinum-nickel alloy excavated nano-multipods with hexagonal close-packed structure and superior activity towards hydrogen evolution reaction.

Crystal phase regulations may endow materials with enhanced or new functionalities. However, syntheses of noble metal-based allomorphic nanomaterials are extremely difficult, and only a few successful examples have been found. Herein, we report the discovery of hexagonal close-packed Pt-Ni alloy, despite the fact that Pt-Ni alloys are typically crystallized in face-centred cubic structures. The hexagonal close-packed Pt-Ni alloy nano-multipods are synthesized via a facile one-pot solvothermal route, where the branches of nano-multipods take the shape of excavated hexagonal prisms assembled by six nanosheets of 2.5 nm thickness. The hexagonal close-packed Pt-Ni excavated nano-multipods exhibit superior catalytic property towards the hydrogen evolution reaction in alkaline electrolyte. The overpotential is only 65 mV versus reversible hydrogen electrode at a current density of 10 mA cm-2, and the mass current density reaches 3.03 mA µgPt-1 at -70 mV versus reversible hydrogen electrode, which outperforms currently reported catalysts to the best of our knowledge.

Quality of life and cosmetic result of single-port access endoscopic thyroidectomy via axillary approach in patients with papillary thyroid carcinoma.

BACKGROUND: Endoscopic thyroidectomy for minimally invasive thyroid surgery has been widely applied in the past decade. The present study aimed to evaluate the effects of single-port access transaxillary totally endoscopic thyroidectomy on the postoperative outcomes and functional parameters, including quality of life and cosmetic result in patients with papillary thyroid carcinoma (PTC). PATIENTS AND METHODS: Seventy-five patients with PTC who underwent endoscopic thyroidectomy via a single-port access transaxillary approach were included (experimental group). A total of 123 patients with PTC who were subjected to conventional open total thyroidectomy served as the control group. The health-related quality of life and cosmetic and satisfaction outcomes were assessed postoperatively. RESULTS: The mean operation time was significantly increased in the experimental group. The physiological functions and social functions in the two groups were remarkably augmented after 6 months of surgery. However, there was no significant difference in the scores of speech and taste between the two groups at the indicated time of 1 month and 6 months. In addition, the scores for appearance, satisfaction with appearance, role-physical, bodily pain, and general health in the experimental group were better than those in the control group at 1 month and 6 months after surgery. CONCLUSION: The single-port access transaxillary totally endoscopic thyroidectomy is safe and feasible for the treatment of patients with PTC. The subjects who underwent this technique have a good perception of their general state of health and are likely to participate in social activities. It is worthy of being clinically used for patients with PTC.

MALAT1 promotes the proliferation and invasion of thyroid cancer cells via regulating the expression of IQGAP1.

BACKGROUND: Increasing evidence indicated that metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) acted as a key regulator in the proliferation and invasion of several cancers. However, the function of MALAT1 in the development of thyroid cancer has not been experimentally established. METHODS: The expression of MALAT1 and IQGAP1 in thyroid cancer tissues and cells were detected by quantitative real-time PCR and western blot. The effects of MALAT1 and IQGAP1 on the cell proliferation and invasion of thyroid cancer cells were detected with a 3-(4,5-dimethylthiazol)-2,5-diphenyl tetrazolium 4 (MTT) assay and a Transwell assay, respectively. FTC-133 or SW1736 transfected with si-MALAT1 or pcDNA-MALAT1 were injected subcutaneously into 4-week-olds BALB/c mice to examine the impact of MALAT1 on the tumor development of thyroid cancer in vivo. RESULTS: In this study, we discovered the higher level of MALAT-1 and expression of IQGAP1 in thyroid cancer tissues and in thyroid cancer cells compared to that in the control. MTT and Transwell assay showed that the proliferation and invasion of FTC-133 cells with MALAT-1 knockdown were inhibited. Moreover, MALAT-1 could upregulate the expression of IQGAP1 in thyroid cancer cells. In addition, IQGAP1 knockdown reversed the decreasing cell proliferation and invasion of thyroid cancer induced by MALAT-1 overexpression. Finally, the study in vivo verified that MALAT-1 promoted the tumor growth of thyroid cancer. CONCLUSION: Our study indicated that MALAT1 promoted the proliferation and invasion of thyroid cancer cells via regulating the expression of IQGAP1.

Hydrogen adsorption-mediated synthesis of concave Pt nanocubes and their enhanced electrocatalytic activity.

Concave nanocubes are enclosed by high-index facets and have negative curvature; they are expected to have enhanced reactivity, as compared to nanocubes with flat surfaces. Herein, we propose and demonstrate a new strategy for the synthesis of concave Pt nanocubes with {hk0} high-index facets, by using a hydrogen adsorption-mediated electrochemical square-wave potential method. It was found that Pt atoms prefer to deposit on edge sites rather than terrace sites on Pt surfaces with intensive hydrogen adsorption, resulting in the formation of concave structures. The as-prepared concave Pt nanocubes exhibit enhanced catalytic activity and stability towards oxidation of ethanol and formic acid in acidic solutions, compared to commercial Pt/C catalysts.