Preparation and photoelectrochemical performance of PbSe/BaTiO3/TiO2 composite film

By dipping-lifting in sol–gel solution and reducing process, the TiO₂ composite film on the glass plate was first prepared. Then, the PbSe/BaTiO₃/TiO₂ composite film was fabricated by interface reaction with BaTiO₃ and PbSe on the surface of TiO₂ composite film. The characterization results show that the uniform porous TiO₂ film is made up of the anatase crystal, and the PbSe/BaTiO₃/TiO₂ composite film is constructed by doping or depositing BaTiO₃ and PbSe nanoparticles on the surface of TiO₂ film. The photoelectrochemical measurement results indicate that the PbSe/BaTiO₃/TiO₂ composite film has an interesting photoelectrochemical conversion property.     

Elementary Photoelectronic Processes at a Porphyrin Dye/Single‐Walled TiO2 Nanotube Hetero‐interface in Dye‐Sensitized Solar Cells: A First‐Principles Study

A unique one‐dimensional (1D) sandwich single‐walled TiO₂ nanotube (STNT) is proposed as a photoanode nanomaterial with perfect morphology and large specific surface area. We have thoroughly examined the elementary photoelectronic processes occurring at the porphyrin dye/STNT hetero‐interface in dye‐sensitized solar cells (DSSCs) by theoretical simulation. It is desirable to investigate the interfacial photoelectronic processes to elucidate the electron transfer and transport mechanism in 1D STNT‐based DSSCs. We have found that the photoexcitation and interfacial charge separation mechanism can be described as follows. A ground‐state electron of the dye molecule (localized around the electron donor) is first promoted to the excited state (distributed electron donor), and then undergoes ultrafast injection into the conduction band of the STNT, leaving a hole around the oxidized dye. Significantly, the injected electron in the conduction band is transported along the STNT by means of Ti 3d orbitals, offering a unidirectional electron pathway toward the electrode for massive collection without the observation of trap states. Our study not only provides theoretical guidelines for the modification of TiO₂ nanotubes as a photoanode material, but also opens a new perspective for the development of a novel class of TiO₂ nanotubes with high power‐generation efficiency.     

A Triazatruxene‐Based Glycocluster as a Fluorescent Sensor for Concanavalin A

A new triazatruxene‐based fluorescent glycocluster has been designed, synthesized, and fully characterized by NMR spectroscopy and mass spectrometry. Furthermore, its specific and selective binding properties with concanavalin A (Con A) have been investigated by fluorescence spectroscopy, circular dichroism (CD) spectroscopy, and turbidity assay. The obtained results showed that the multivalent mannose‐modified triazatruxene exhibited specific binding with Con A, but no binding to peanut agglutinin (PNA) lectin or bovine serum albumin (BSA), corresponding to a two‐orders‐of‐magnitude higher affinity than that of monovalent mannose ligands. Most interestingly, a fluorescence enhancement of the triazatruxene‐based glycocluster was observed upon binding with Con A because of hydrophobic interactions involving sites close to the triazatruxene moiety. Furthermore, the inhibitory ability of the triazatruxene‐based glycocluster against ORN178‐ induced haemagglutination has been investigated by haemagglutination inhibition assay. The results indicated selective binding with ORN178.     

Instant Visual Detection of Picogram Levels of Trinitrotoluene by Using Luminescent Metal–Organic Framework Gel‐Coated Filter Paper

There is an ongoing need for explosive detection strategies to uncover threats to human security including illegal transport and terrorist activities. The widespread military use of the explosive trinitrotoluene (TNT) for landmines poses another particular threat to human health in the form of contamination of the surrounding environment and groundwater. The detection of explosives, particularly at low picogram levels, by using a molecular sensor is seen as an important challenge. Herein, we report on the use of a fluorescent metal–organic framework hydrogel that exhibits a higher detection capability for TNT in the gel state compared with that in the solution state. A portable sensor prepared from filter paper coated by the hydrogel was able to detect TNT at the picogram level with a detection limit of 1.82 ppt (parts per trillon). Our results present a simple and new means to provide selective detection of TNT on a surface or in aqueous solution, as afforded by the unique molecular packing through the metal–organic framework structure in the gel formation and the associated photophysical properties. Furthermore, the rheological properties of the MOF‐based gel were similar to those of a typical hydrogel.     

Atomic‐Level Alloying and De‐alloying in Doped Gold Nanoparticles

Atomically precise alloying and de‐alloying processes for the formation of Ag–Au and Cu–Au nanoparticles of 25‐metal‐atom composition (referred to as Ag_xAu_25?x(SR)₁₈ and Cu_xAu_25?x(SR)₁₈, in which R=CH₂CH₂Ph) are reported. The identities of the particles were determined by matrix‐assisted laser desorption ionization mass spectroscopy (MALDI‐MS). Their structures were probed by fragmentation analysis in MALDI‐MS and comparison with the icosahedral structure of the homogold Au₂₅(SR)₁₈ nanoparticles (an icosahedral Au₁₃ core protected by a shell of Au₁₂(SR)₁₈). The Cu and Ag atoms were found to preferentially occupy the 13‐atom icosahedral sites, instead of the exterior shell. The number of Ag atoms in Ag_xAu_25?x(SR)₁₈ (x=0–8) was dependent on the molar ratio of Ag^I/Au^III precursors in the synthesis, whereas the number of Cu atoms in Cu_xAu_25?x(SR)₁₈ (x=0–4) was independent of the molar ratio of Cu^II/Au^III precursors applied. Interestingly, the Cu_xAu_25?x(SR)₁₈ nanoparticles show a spontaneous de‐alloying process over time, and the initially formed Cu_xAu_25?x(SR)₁₈ nanoparticles were converted to pure Au₂₅(SR)₁₈. This de‐alloying process was not observed in the case of alloyed Ag_xAu_25?x(SR)₁₈ nanoparticles. This contrast can be attributed to the stability difference between Cu_xAu_25?x(SR)₁₈ and Ag_xAu_25?x(SR)₁₈ nanoparticles. These alloyed nanoparticles are promising candidates for applications such as catalysis.     

Microenvironment Effects in Electrocatalysis: Ionic‐Liquid‐Like Coating on Carbon Nanotubes Enhances the Pd‐Electrocatalytic Alcohol Oxidation

A new catalyst consisting of ionic liquid (IL)‐functionalized carbon nanotubes (CNTs) obtained through 1,3‐dipolar cycloaddition support‐enhanced electrocatalytic Pd nanoparticles (Pd@IL(Cl^?)‐CNTs) was successfully fabricated and applied in direct ethanol alkaline fuel cells. The morphology, structure, component and stability of Pd@IL(Cl^?)‐CNTs were systematic characterized by transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM), Raman spectra, thermogravimetric analysis (TGA) and X‐ray diffraction (XRD). The new catalyst exhibited higher electrocatalytic activity, better tolerance and electrochemical stability than the Pd nanoparticles (NPs) immobilized on CNTs (Pd@CNTs), which was ascribed to the effects of the IL, larger electrochemically active surface area (ECSA), and greater processing performance. Cyclic voltammograms (CVs) at various scan rates illustrated that the oxidation behaviors of ethanol at all electrodes were controlled by diffusion processes. The investigation of the different counteranions demonstrated that the performance of the IL‐CNTs hybrid material was profoundly influenced by the subtly varied structures of the IL moiety. All the results indicated that the Pd@IL(Cl^?)‐CNTs catalyst is an efficient anode catalyst, which has potential applications in direct ethanol fuel cells and the strategy of IL functionalization of CNTs could be available to prepare other carbonaceous carrier supports to enhance the dispersivity, stability, and catalytic performance of metal NPs as well.     

Electrospun Porous NiCo2O4 Nanotubes as Advanced Electrodes for Electrochemical Capacitors

Novel, porous NiCo₂O₄ nanotubes (NCO‐NTs) are prepared by a single‐spinneret electrospinning technique followed by calcination in air. The obtained NCO‐NTs display a one‐dimensional architecture with a porous structure and hollow interiors. The effect of precursor concentration on the morphologies of the products is investigated. Due to their unique structure, the prepared NCO‐NT electrode exhibits a high specific capacitance (1647 F g^?1 at 1 A g^?1), excellent rate capability (77.3 % capacity retention at 25 A g^?1), and outstanding cycling stability (6.4 % loss after 3000 cycles), which indicates it has great potential for high‐performance electrochemical capacitors. The desirable enhanced capacitive performance of NCO‐NTs can be attributed to the relatively large specific surface area of these porous and hollow one‐dimensional nanostructures.     

Synthesis of Poly(benzothiadiazole‐co‐dithienobenzodithiophenes) and Effect of Thiophene Insertion for High‐Performance Polymer Solar Cells

We describe herein the synthesis of novel donor–acceptor conjugated polymers with dithienobenzodithiophenes (DTBDT) as the electron donor and 2,1,3‐benzothiadiazole as the electron acceptor for high‐performance organic photovoltaics (OPVs). We studied the effects of strategically inserting thiophene into the DTBDT as a substituent on the skeletal structure on the opto‐electronic performances of fabricated devices. From UV/Vis absorption, electrochemical, and field‐effect transistor analyses, we found that the thiophene‐containing DTBDT derivative can substantially increase the orbital overlap area between adjacent conjugated chains and thus dramatically enhance charge‐carrier mobility up to 0.55 cm² V^?1 s^?1. The outstanding charge‐transport characteristics of this polymer allowed the realization of high‐performance organic solar cells with a power conversion efficiency (PCE) of 5.1 %. Detailed studies on the morphological factors that enable the maximum PCE of the polymer solar cells are discussed along with a hole/electron mobility analysis based on the space‐charge‐limited current model.     

Controllable Syntheses of Porous Metal–Organic Frameworks: Encapsulation of LnIII Cations for Tunable Luminescence and Small Drug Molecules for Efficient Delivery

Two porous metal–organic frameworks (MOFs), [Zn₃(L)(H₂O)₂] ? 3 DMF ? 7 H₂O ( MOF‐1 ) and [(CH₃)₂NH₂]₆[Ni₃(L)₂(H₂O)₆] ? 3 DMF ? 15 H₂O ( MOF‐2 ), were synthesized solvothermally (H₆L=1,2,3,4,5,6‐hexakis(3‐carboxyphenyloxymethylene)benzene). In MOF ‐ 1 , neighboring Zn^II trimers are linked by the backbones of L ligands to form a fascinating 3D six‐connected framework with the point symbol (4¹².6³) (4¹².6³). In MOF‐2 , eight L ligands bridge six Ni^II atoms to generate a rhombic‐dodecahedral [Ni₆L₈] cage. Each cage is surrounded by eight adjacent ones through sharing of carboxylate groups to yield an unusual 3D porous framework. Encapsulation of Ln^III cations for tunable luminescence and small drug molecules for efficient delivery were investigated in detail for MOF‐1 .     

“One pot” homogeneous synthesis of thermoplastic cellulose acetate-graft-poly(l-lactide) copolymers from unmodified cellulose

Using native cellulose as the starting material, cellulose acetate-graft-ploy (l-lactide) (CA-g-PLA) copolymers were successfully synthesized by “one-pot” process in an ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl). In this process, cellulose was first reacted with acetic anhydride, yielding cellulose acetate (CA), and then ring opening graft copolymerization of l-lactide was carried out from the residual hydroxyl groups of CA in the same solution using 4-dimethylaminopridine (DMAP) as the catalyst. Both acetyl and ploy (l-lactide) contents in CA-g-PLA copolymers could be well controlled by changing reaction conditions. The structures and thermal properties of CA-g-PLA copolymers were characterized. The glass transition temperature T_g of copolymers decreased with increasing PLA content. Compared to the pure PLA and cellulose-graft-PLA copolymers, the CA-g-PLA copolymers possessed better thermo mechanical properties in a temperature range of 60–130 °C. When the molar substitution of PLA (MS_PLA) was above 1.71, the CA-g-PLA copolymers exhibited thermoplastic behavior and could be processed by conventional thermal processing methods, such as injection molding and melt spinning.