Investigation of non-precious metal cathode catalysts for direct borohydride fuel cells.

Borohydride crossover in anion exchange membrane (AEM) based direct borohydride fuel cells (DBFCs) impairs their performance and induces cathode catalyst poisoning. This study evaluates three non-precious metal catalysts, namely LaMnCoO (LMCO) perovskite, MnCoO (MCS) spinel, and Fe-N-C, for their application as cathode catalysts in DBFCs. The rotating disk electrode (RDE) testing shows significant borohydride tolerance of MCS.

High-Performance Zinc-Air Batteries Based on Bifunctional Hierarchically Porous Nitrogen-Doped Carbon.

Active and durable bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) on the cathode are required for high-performance rechargeable metal-air batteries. Herein, the synthesis of hierarchically porous nitrogen-doped carbon (HPNC) with bifunctional oxygen electrocatalysis for Zn-air batteries is reported. The HPNC catalyst possesses a large surface area of 1459 m g and exhibits superior electrocatalytic activity toward ORR and OER simultaneously with a low OER/ORR overpotential of 0.

Construction of multilayer films with bactericidal and long-term antitumor drug release properties as a non-vascular stent coating for therapy in obstruction.

The construction of antibacterial and antitumor coatings could offer effective routes to improve the therapeutic effects of non-vascular stents for unresectable obstructions caused by malignant tumours. Herein, polyelectrolyte multilayers have been explored as bactericidal coatings with controlled antitumor drug release. To solve the challenges of loading and controlled release of small-molecule chemotherapeutic drugs in polyelectrolyte multilayers, the antitumor drug doxorubicin (DOX) was chemically conjugated onto polyethylenimine via cis aconitic anhydride (pH-sensitive linker), thus obtaining the polycation prodrug PEI-CA-DOX.

Diameter of Carbon Nanotube-Directed Self-Assembly of Amphiphilic Block Copolymers.

The cooperative self-assembly of nanoparticles and amphiphilic block copolymers has attracted increasing interests as it offers effective routes to achieve nanocomposite supramolecular structures with desired structure and properties. The incorporation of nanoparticles usually tunes the self-assembly structure of block copolymers, as the copolymer-nanoparticle interactions may change the relative volume ratio of hydrophobic block/hydrophilic block copolymers. It should be noted that the micro-size length and the strong nonpolar feature of carbon nanotubes (CNTs) may cause the block copolymer-CNT interactions to differ from the the block copolymer-nanoparticle interactions.

Preparation and Investigation of Amphiphilic Block Copolymers/Fullerene Nanocomposites as Nanocarriers for Hydrophobic Drug.

Biopolymer/inorganic material nanocomposites have attracted increasing interest as nanocarriers for delivering drugs owing to the combined advantages of both biopolymer and inorganic materials. Here, amphiphilic block copolymer/fullerene nanocomposites were prepared as nanocarriers for hydrophobic drug by incorporation of C60 in the core of methoxy polyethylene glycol-poly(d,l-lactic acid) (MPEG-PDLLA) micelles. The structure and morphology of MPEG-PDLLA/C60 nanocomposites were characterized using transmission electron microscopy, dynamic light scattering, high-resolution transmission electron microscopy, and thermal gravimetric analysis.

Atomic-Scale Insight into Tautomeric Recognition, Separation, and Interconversion of Guanine Molecular Networks on Au(111).

Although tautomerization may directly affect the chemical or biological properties of molecules, real-space investigation on the tautomeric behaviors of organic molecules in a larger area of molecular networks has been scarcely reported. In this paper, we choose guanine (G) molecule as a model system. From the interplay of high-resolution scanning tunneling microscopy (STM) imaging and density functional theory (DFT) calculations, we have successfully achieved the tautomeric recognition, separation, and interconversion of G molecular networks (formed by two tautomeric forms G/9H and G/7H) with the aid of NaCl on the Au(111) surface in ultrahigh vacuum (UHV) conditions.

Solventless Formation of G-Quartet Complexes Based on Alkali and Alkaline Earth Salts on Au(111).

Template cations have been extensively employed in the formation, stabilization and regulation of structural polymorphism of G-quadruplex structures in vitro. However, the direct addition of salts onto solid surfaces, especially under ultra-high-vacuum (UHV) conditions, to explore the feasibility and universality of the formation of G-quartet complexes in a solventless environment has not been reported. By combining UHV-STM imaging and DFT calculations, we have shown that three different G-quartet-M (M: Na/K/Ca) complexes can be obtained on Au(111) using alkali and alkaline earth salts as reactants.

Controllable Scission and Seamless Stitching of Metal-Organic Clusters by STM Manipulation.

Scanning tunneling microscopy (STM) manipulation techniques have proven to be a powerful method for advanced nanofabrication of artificial molecular architectures on surfaces. With increasing complexity of the studied systems, STM manipulations are then extended to more complicated structural motifs. Previously, the dissociation and construction of various motifs have been achieved, but only in a single direction.

Dehydrogenative homocoupling of terminal alkenes on copper surfaces: a route to dienes.

Homocouplings of hydrocarbon groups including alkynyl (sp(1) ), alkyl (sp(3) ), and aryl (sp(2) ) have recently been investigated on surfaces with the interest of fabricating novel carbon nanostructures/nanomaterials and getting fundamental understanding. Investigated herein is the on-surface homocoupling of an alkenyl group which is the last elementary unit of hydrocarbons. Through real-space direct visualization (scanning tunneling microscopy imaging) and density functional theory calculations, the two terminal alkenyl groups were found to couple into a diene moiety on copper surfaces, and is contrary to the common dimerization products of alkenes in solution.

On-surface formation of two-dimensional polymer via direct C-H activation of metal phthalocyanine.

From high-resolution UHV-STM imaging and DFT calculations we successfully obtained a 2D polymer structure formed through direct C-H activation followed by an aryl-aryl coupling of a metal-phthalocyanine (CoPc) on Ag(110).

Formation of polyphenyl chains through hierarchical reactions: Ullmann coupling followed by cross-dehydrogenative coupling.

From an interplay of UHV-STM imaging and DFT calculations, we have illustrated on-surface formation of polyphenyl chains through a hierarchical reaction pathway involving two different kinds of reactions (Ullmann coupling and cross-dehydrogenative coupling), which will provide a deeper understanding of on-surface chemical reactions and an alternative and efficient strategy to fabricate desired surface molecular nanostructures.

On-surface synthesis of organometallic complex via metal-alkene interactions.

From the interplay of high-resolution scanning tunneling microscopy (STM) imaging/manipulation and density functional theory (DFT) calculations, we have shown that the spontaneous formation of an organometallic complex by copper-alkene interactions can be successfully achieved, where the specific molecular adsorption geometry is revealed to be the key for facilitating such interaction.

Formation of a G-quartet-Fe complex and modulation of electronic and magnetic properties of the Fe center.

Although the G-quartet structure has been extensively investigated due to its biological importance, the formation mechanism, in particular, the necessity of metal centers, of an isolated G-quartet on solid surfaces remains ambiguous. Here, by using scanning tunneling microscopy under well-controlled ultra-high-vacuum conditions and density functional theory calculations we have been able to clarify that besides the intraquartet hydrogen bonding a metal center is mandatory for the formation of an isolated G-quartet. Furthermore, by subtly perturbing the local coordination bonding schemes within the formed G-quartet complex via local nanoscale scanning tunneling microscopy manipulations, we succeed in modulating the d orbitals and the accompanying magnetic properties of the metal center.

Oxygen-induced self-assembly of quaterphenyl molecules on metal surfaces.

From high-resolution UHV-STM imaging and DFT calculations we have demonstrated a novel method to construct well-ordered molecular nanostructures of an unfunctionalized aromatic molecule (4Ph) on both Ag(110) and Cu(110) by introducing oxygen molecules.

On-surface aryl-aryl coupling via selective C-H activation.

Through the interplay of high-resolution scanning tunneling microscopy (STM) imaging/manipulation and density functional theory (DFT) calculations, we have demonstrated that an unprecedented selective aryl-aryl coupling via direct C-H bond activation can be successfully achieved on Cu(110). These findings present a simple and generalized route for preparing low dimensional carbon nanomaterials.

Adsorption-geometry induced transformation of self-assembled nanostructures of an aldehyde molecule on Cu(110).

From an interplay of high-resolution STM imaging/manipulation and DFT calculations, we have revealed that different self-assembled nanostructures of BA molecules on Cu(110) are attributable to specific molecular adsorption geometries, and thus the corresponding intermolecular hydrogen bonding patterns. The STM manipulations demonstrate the feasibility of switching such weak-hydrogen-bonding patterns.

Ni-induced supramolecular structural transformation of cytosine on Au(111): from one-dimensional chains to zero-dimensional clusters.

Interplay between high-resolution STM imaging and DFT calculations demonstrates that through introduction of Ni atoms the self-assembled structures of cytosine could undergo a structural transformation from 1-D chains to 0-D clusters on Au(111). Interestingly, the 0-D clusters formed are separately distributed on the surface.

Atomic-scale investigation on the facilitation and inhibition of guanine tautomerization at Au(111) surface.

Nucleobase tautomerization might induce mismatch of base pairing. Metals, involved in many important biophysical processes, have been theoretically proven to be capable of affecting tautomeric equilibria and stabilities of different nucleobase tautomers. However, direct real-space evidence on demonstrating different nucleobase tautomers and further revealing the effect of metals on their tautomerization at surfaces has not been reported to date.

Investigation of thermo-sensitive amphiphilic micelles as drug carriers for chemotherapy in cholangiocarcinoma in vitro and in vivo.

Cholangiocarcinoma is an epithelial cancer of the bile ducts with poor prognosis and, in recent years, a rapidly increasing incidence. In this study, nano-sized thermo-sensitive micelles were investigated as drug carriers to improve chemotherapy in cholangiocarcinoma. Thermo-sensitive amphiphilic block copolymer, P-(N,N-isopropylacrylamide-co-N-hydroxymethylacrylamide)-b-caprolactone [P-(NIPAAm-co-NHMAAm)-b-PCL] with lower critical solution temperature (LCST) at about 38°C was synthesized.

Surface-assisted cis-trans isomerization of an alkene molecule on Cu(110).

From the interplay of STM imaging and DFT calculations we have investigated the isomerization of an alkene molecule on Cu(110) under ultrahigh vacuum conditions. We show that the on-surface cis-trans isomerization could efficiently occur well below room temperature, in which the copper surface is speculated to play a key role.

Tailoring on-surface supramolecular architectures based on adenine directed self-assembly.

From an interplay of high-resolution scanning tunneling microscopy (STM) imaging and density functional theory (DFT) calculations we demonstrate that by delicately choosing the parent molecule (adenine) we are able to tune the self-assembled nanostructures of adenine derivatives which are directed by the specific intermolecular interactions provided by the adenine moiety.

Atomic-scale structures and interactions between the guanine quartet and potassium.

The atomic-scale identification of the G4K1 structural motif is achieved using an interplay of STM imaging and DFT calculations. Its high stability is found to be caused by the delicate balance between hydrogen bonding and metal-ligand interaction, which is of utmost relevance to model interactions of the G-quadruplex with cations in vivo.

Identification of molecular-adsorption geometries and intermolecular hydrogen-bonding configurations by in situ STM manipulation.

Don't be dim! By combining the technique with DFT calculations, STM manipulation was extended to the probing of intermolecular hydrogen-bonding configurations in self-assembled nanostructures. It was also possible to convert one configuration into another in a controlled fashion through the careful manipulation of a particular structural unit (see picture).

On-surface formation of one-dimensional polyphenylene through Bergman cyclization.

On-surface fabrication of covalently interlinked conjugated nanostructures has attracted significant attention, mainly because of the high stability and efficient electron transport ability of these structures. Here, from the interplay of scanning tunneling microscopy imaging and density functional theory calculations, we report for the first time on-surface formation of one-dimensional polyphenylene chains through Bergman cyclization followed by radical polymerization on Cu(110). The formed surface nanostructures were further corroborated by the results for the ex situ-synthesized molecular product after Bergman cyclization.

A molecular conformational change induced self-assembly: from randomness to order.

From an interplay of high-resolution scanning tunneling microscopy (STM) imaging and density functional theory (DFT) calculations we reveal how a molecular conformational change induced self-assembly process can result in the conversion from a random molecular phase to the formation of two types of ordered surface nanostructures with different apparent heights.