Search

Direct alcohol fuel cells represent a promising green and sustainable route for chemical to electrical energy conversion; however, designing highly efficient electrocatalysts for the electro-oxidat...

Cache-type phase-change random-access memory is a remaining challenge on the path to universal memory. The recently designed Sc0.2Sb2Te3 (SST) alloy is one of the most promising phase-change materi...

Generally, the electron-withdrawing substitution on the end-capping group of the acceptor–donor–acceptor type small-molecule acceptor (SMA) narrows the optical bandgap, and the electron-donating group lifts the lowest unoccupied molecular orbital (LUMO) energy level of nonfullerene SMA, which increase the short-circuit current density (JSC) and open circuit voltage (VOC) of the organic solar cells (OSCs), respectively; however, their synergistic effect on the properties of SMA has remained elusive. Here, we first report a new end-capping group (EG), namely, 5-fluoro-6-methyl-3-dicycanovinylindan-1-one (CFDCI), that concurrently possesses an electron-withdrawing fluorine substitute and an electron-donating methyl group. A prototype SMA (namely, ITCF) based on CFDCI and its two control counterparts were prepared to fully understand the structure–property relationship that the new EG exerts on the resultant SMA. The ITCF demonstrated a moderately crystalline morphology in pristine film and more balanced char...

ortho-Linkages are effective in improving the performance of organic light-emitting diode (OLED) materials but may weaken the local chemical bonds and even incur chemical degradation due to bond cleavage reactions in operating OLEDs, especially for blue-emitting materials. Here, we conducted a systematic theoretical study on a series of carbazole (Cz)-based molecules with typical donor (D)−π−acceptor (A) structures to investigate the influence of ortho-substituents on the bond dissociation energies (BDEf) of their fragile D−π bonds (i.e., C–N bonds), where “fragile” means that the bonds have the minimum or a comparable-to-the-minimum BDE in the molecule. Through calculations, it was found that different substituents or even the same substituent on different sites of the molecule could bring variable effects on the polar D−π bond. Specifically, in the π-group, the effects of a substituent on BDEf mainly depend on the steric hindrance that it brings to the D−π bond. Thus, ortho-CH3 groups hardly affect BDEf...

The introduction of multiple components into one crystalline metal–organic framework (MOF) provides a feasible approach to fully understand the correlation of component heterogeneity and the whole performance. Herein, photoactive tetratopic chlorin (TCPC) ligands with different geometry and connectivity have been successfully incorporated into the Hf-UiO-66 archetype structure without altering the underlying topology by a facile strategy. Unlike previous porphyrin-nanoscale-MOFs (porphyrin-NMOFs) with homogeneous periodical porphyrin arrangements typically for photodynamic therapy (PDT) usage, we demonstrate that TCPC component heterogeneity within as-synthesized TCPC-UiO possesses both PDT and photothermal therapy (PTT) simultaneously, but PTT takes a more potent antitumor efficacy as proven in several photophysical characterizations and biological experiments in vitro. The high photothermal conversion efficiency, favorable photostability and biocompatibility, and strong X-ray attenuating ability of the ...

Among the most efficient strategies to boost the electrochemical sensing and catalysis of Pt-based multimetallic nanomaterials is atomically manipulating the surface and near-surface nanostructures, which directly govern the adsorption behavior. Using one-dimensional PtCo urchin-like nanowires as the platform, we herein achieve the construction of high-index faceted Pt-skin configuration. Such unique structure shows excellent electrocatalytic performance toward the electrochemical detection of various molecules (H2O2, NH2NH2, dopamine, and acetaminophen), with the capability of real-time monitoring of H2O2 released from living cells and an impressive detection limit of 0.4 nM. Meanwhile, the combination of high-index facet and Pt-skin architecture also enables enhanced catalytic activity for the electro-reduction of oxygen in acid, realizing a very high mass activity of 2.2 A/mgPt. Our study demonstrates the great potential of surface and near-surface engineering at the atomic level in promoting the elect...

Nanosized electrodes for Li-ion batteries typically display improved electrochemical properties, which are generally attributed to the reduced dimensionality for lithiation. However, the intriguing roles of surface defects and disorder associated with the nanosized materials are often overlooked. Here, combining atomically resolved structural analysis with density functional theory calculations, we reveal that the formation of intrinsic oxygen vacancies near surface in silver hollandite nanorods modifies the local atomic structure and valence state. These surface reconstructions resulted from oxygen vacancies can significantly affect the diffusion pathways in what are otherwise one-dimensional (1D) tunneled structures. On the basis of energy barrier calculations, we demonstrate that the oxygen vacancies boost ionic transport through the edge sharing MnO6 polyhedra in the a–b plane. Thus, within a single rod different from the inherent 1D tunnel diffusion in the interior, the ionic transport at oxygen vaca...

Due to the unique optical properties, colloidal quantum dots (QDs) are excellent candidates for developing next-generation display and solid-state lighting technologies. However, some factors including photoluminescence blinking and Forster resonance energy transfer (FRET) still affect their practical applications. Herein, a series of ZnCdSe-based core/shell QDs with low optical polydispersity have been successfully synthesized by a “low-temperature injection and high-temperature growth” precisely controlled method. The alloyed ZnCdSe core with a certain ratio of Cd and Zn was presynthesized first. Followed by accurate ZnS shell growth, the as-synthesized core/shell QDs are nonblinking with the nonblinking threshold volume of ∼137 nm3. The PL decay dynamics are all single-exponential for both QDs in solutions and close-packed solid films when ZnS shell thickness varying from 2 to 20 monolayers. FRET can be effectively suppressed after growing 10 monolayers of ZnS shell. All of these superb characteristics...

The mixed metal Pb/Sn halide perovskites have drawn significant attentions in perovskite photovoltaics due to their broad absorption spectra and tunable band gaps. To obtain a deeper understanding of these materials properties, single crystals are regarded as the best platform among various building blocks for fundamental study. Here, we report the mixed-metal MAPbxSn1–xBr3 (MA = CH3NH3) perovskite single crystals grown by top seeded solution growth (TSSG) method. Systematical characterizations were applied to investigating their structures and optoelectronic properties. These single crystals kept higher stability even exposed to air over one month than that of MASnBr3. The outstanding electrical properties, such as lower trap-state density and higher carrier mobility, were investigated by space charge-limited current (SCLC) and the Hall Effect measurements. More importantly, these perovskite single crystals exhibited much narrower optical band gap (1.77 eV) and longer carrier lifetime (∼2 μs) than those ...

Doped motifs offer an intriguing structural pathway toward improving conductivity for battery applications. Specifically, Ca-doped, three-dimensional “flower-like” Li4–xCaxTi5O12 (“x” = 0, 0.1, 0.15, and 0.2) micrometer-scale spheres have been successfully prepared for the first time using a simple and reproducible hydrothermal reaction followed by a short calcination process. The products were experimentally characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) mapping, inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge testing. Calcium dopant ions were shown to be uniformly distributed within the LTO structure without altering the underlying “flower-like” morphology. The largest lattice expansion and the highest Ti3+ ratios were noted ...

Solution-processable organic semiconductors have potentials as visible photoelectrochemical (PEC) water splitting photoelectrodes due to their tunable small band gap and electronic energy levels, but they are typically limited by poor stability and photocatalytic activity. Here, we demonstrate the direct visible PEC water oxidation on solution-processed organic semiconductor thin films with improved stability and performance by ultrathin metal oxide passivation layers. N-type fullerene-derivative thin films passivated by sub-2 nm ZnO via atomic layer deposition enabled the visible PEC water oxidation at wavelengths longer than 600 nm in harsh alkaline electrolyte environments with up to 30 μA/cm2 photocurrents at the thermodynamic water-oxidation equilibrium potential and the photoanode half-lifetime extended to ∼1000 s. The systematic investigation reveals the enhanced water oxidation catalytic activity afforded by ZnO passivation and the charge tunneling governing the hole transfer through passivation l...

Excellent durable antifogging film, which is composed of hollow microspheres and ZnO nanorods, is fabricated via combining airless spray and crystal growth methods. Because the thermal insulation effect of hollow microspheres strengthens the superhydrophobicity of the micro- and nanostructure composite film at lower temperatures, durable antifogging is realized successfully. When the film is placed in a low-temperature, high-humidity environment, supercooled tiny water droplets cannot spread on it and can easily coalesce and jump off from the surface, exhibiting the robust superhydrophobic and antifogging performance for a significantly long time. This investigation provides insight into designing structured thermal insulation surface materials to realize antifogging that can be applied into microdevices used in cold, high-humidity environments.

The limitation for the biomedical application of porous organic polymers (POPs) is the big size and poor dispersibility in aqueous media. Herein, a nanoscale metal–organic framework (MOF)@POP composite, named UNM, has been synthesized by epitaxial growth of the photoactive porphyrin-POPs (H2P-POP) on the outer surface of amine containing UiO-66 (UiO-AM). After the growth of POPs, the crystallization, pore structure, and size distribution of UNM are retained well. The formed UNM possesses a small size of less than 200 nm and could be internalized by cancer cells. Such light-activated UNM exhibits efficient ability to generate 1O2 under various experimental conditions, which can be further applied for PDT efficacy. The present work demonstrates the great potential of nanoscale porous polymers in biomedical fields and cancer treatment.

The hybrid perovskites with special optoelectronic properties have attracted more attention to the scientific and industrial applications. However, because of the toxicity and instability of lead complexes, there is interest in finding a nontoxic substitute for the lead in the halides perovskites and solving the ambiguous crystal structures and phase transition of NH(CH3)3SnX3 (X = Cl, Br). Here, we report the bulk crystal growths and different crystal morphologies of orthorhombic hybrid perovskites NH(CH3)3SnX3 (X = Cl, Br) in an ambient atmosphere by bottom-seeded solution growth (BSSG) method. More importantly, detailed structural determination and refinements, phase transition, band gap, band structure calculations, nonlinear optical (NLO) properties, XPS, thermal properties, and stability of NH(CH3)3SnX3 (X = Cl, Br) single crystals are demonstrated. NH(CH3)3SnCl3 single crystal undergoes reversible structural transformation from orthorhombic space group Cmc21 (no. 36) to monoclinic space group Cc (n...

The antiperovskite Mn3+xNi1–xN compounds have been synthesized and characterized by a variety of experimental techniques. After Mn doping at the Ni site, both ferromagnetic characteristics and an Invar-like effect were observed in the antiferromagnetic host material. The observed Invar-like behavior was assumed to be related to the characteristic magnetic structure induced by the doping. Neutron diffraction results prove that the Mn doping stabilizes the special Γ5g antiferromagnetic phase with strong spin–lattice coupling that can be tuned to achieve Invar-like behavior. The magnetovolume effect (MVE) and significant correlation between spin and lattice were confirmed for the Γ5g magnetic phase by the first-principles calculations. Moreover, Mn 3d electrons were revealed to be the key factor for the MVE from the calculations. Our study presents a new mechanism for precisely controlling the zero thermal expansion of a single compound by achieving the special Γ5g magnetic phase of Mn atoms.

CaAl2O4:Eu is a persistent luminescence (PL) material in the blue light region with potentially wide commercial applications. With the doping of Nd, the decay time can be elongated to more than 19 h. These excellent properties are believed to be in close relation with the electronic structures of the dopants, the defects, and the host material. In this work, we attempt to achieve a better understanding of the PL mechanism of CaAl2O4:Eu based on first-principles calculations. The electronic structures of the host CaAl2O4, the luminescent center Eu, the O and Ca vacancies, and the dopant Nd are systematically studied. According to the calculations, the 4f and 5d levels of Eu are located within the band gap and slightly above the conduction band minimum (CBM), respectively. The electrons on the 4f levels can be excited into the 5d levels via ultraviolet radiation. The excited electrons on the 5d levels can move to the conduction bands and become free electron carriers. The electron carriers can be trapped fo...

In this report, we synthesize and characterize the structural and optical properties of novel heterostructures composed of (i) semiconducting nanocrystalline CdSe quantum dots (QDs) coupled with (ii) both one- and zero-dimensional (1D and 0D) motifs of self-activated luminescent CaWO4 metal oxides. Specifically, ∼4 nm CdSe QDs have been anchored onto (i) high-aspect ratio 1D nanowires, measuring ∼230 nm in diameter and ∼3 μm in length, as well as onto (ii) crystalline 0D nanoparticles (possessing an average diameter of ∼80 nm) of CaWO4 through the mediation of 3-mercaptopropionic acid (MPA) as a connecting linker. Composite formation was confirmed by complementary electron microscopy and spectroscopy (i.e., IR and Raman) data. In terms of luminescent properties, our results show that our 1D and 0D heterostructures evince photoluminescence (PL) quenching and shortened PL lifetimes of CaWO4 as compared with unbound CaWO4. We propose that a photoinduced electron transfer process occurs from CaWO4 to CdSe QDs...

This paper reports a strategy for controlling surface chemistry of barium titanate (BaTiO3) using surface-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization of an oligothiophene monomer. The modular chemistry on the engineering of nanoparticles provides a facile pathway to compatibilizing dielectric nanofillers in a matrix of oligothiophene polymers, leading to the formation of nanodielectric composites with permittivity at ∼20 and dielectric loss

A novel electron-transporting moiety, 1,2,4-thiadiazole, was first introduced to construct bipolar host molecules for phosphorescent organic light-emitting diodes (PhOLEDs). By incorporating 1,2,4-thiadiazole with typical hole-transporting carbazole moieties, a series of thiadiazole/carbazole hybrids, o-CzTHZ, m-CzTHZ, and p-CzTHZ, were synthesized. All the hybrids exhibit very high glass transition temperatures (Tg ≥ 167 °C) and show good thermal and morphological stability in films. Moreover, these host materials possess good bipolar charge transporting properties; electron and hole mobilities of these bipolar thiadiazole/carbazole hybrids can be tuned by simply adjusting the linkage modes between thiadiazole and carbazole moieties. The maximum external quantum efficiencies (ηEQE, max) in the green PhOLEDs with o-CzTHZ, m-CzTHZ, and p-CzTHZ as the hosts reached 26.1%, 24.0%, and 22.9%, respectively, and their EQE were still over 20% even at the high luminance of 10,000 cd/m2. This study demonstrates tha...

A series of swallow-shaped tetrathiafulvalene (TTF)-based liquid crystal (LC) molecules (a-6TTFn, where 6 represents the number of carbon atoms in the two tails of a-6TTFn and n is the even number of carbon atoms in the alkyl chains attached to the side of the asymmetric TTF mesogen, n = 6−12) was designed and synthesized. One of this series of swallow-shaped asymmetric TTF molecules (abbreviated as a-6TTF12) having 12 carbon atoms in the alkyl chains attached to the side of the asymmetric TTF mesogen served as an example in this study. Major phase transitions and their origins in a-6TTF12 were studied with combined techniques of differential scanning calorimetry (DSC), one-dimensional (1D) wide-angle X-ray diffraction (WAXD) and solid-state carbon-13 (13C) nuclear magnetic resonance (NMR) experiments. a-6TTF12 formed a highly ordered liquid crystalline (ΦLC) phase at higher temperatures and a crystalline (ΦCr) phase at lower temperatures. On the basis of the experimental results, it was found that the hi...

We present an efficient way to calculate the phase diagram of the quaternary Li−Fe−P−O2 system using ab initio methods. The ground-state energies of all known compounds in the Li−Fe−P−O2 system were calculated using the generalized gradient approximation (GGA) approximation to density functional theory (DFT) and the DFT+U extension to it. Considering only the entropy of gaseous phases, the phase diagram was constructed as a function of oxidation conditions, with the oxygen chemical potential, μO2, capturing both temperature and oxygen partial pressure dependence. A modified Ellingham diagram was also developed by incorporating the experimental entropy data of gaseous phases. The phase diagram shows LiFePO4 to be stable over a wide range of oxidation environments, being the first Fe2+-containing phase to appear upon reduction at μO2 = −11.52 eV and the last of the Fe-containing phosphates to be reduced at μO2 = −16.74 eV. Lower μO2 represents more reducing conditions, which generally correspond to higher t...

A new series of mixed-framework compounds in the chalcohalide family has been synthesized using the conventional solid-state reactions. These include CdSb2Se3Br2 1 and its isoelectronic indium derivatives InSb2S4X (X = Cl 2 and Br 3) and InM2Se4Br (M = Sb 4 and Bi 5). Single crystals were grown from direct interaction of stoichiometric mixtures of respective elemental and binary compounds. The parent compound cadmium antimony selenobromide, CdSb2Se3Br2, was synthesized by heating the stoichiometric mixture of CdBr2 and Sb and Se at 450 °C followed by slow cooling. Single-crystal structure analysis was carried out by employing X-ray diffraction methods, showing that this compound crystallizes in the monoclinic crystal system (C2/m, No. 12) with a = 20.998(4) A, b = 4.0260(8) A, c = 12.149(2) A, β = 119.00(3)°, and V = 898.3(3) A3. The framework exhibits mixed CdBr2 and Sb2Se3 sublattices, respectively, adopting the (110) and (100) NaCl-type structures. The former consists of dual octahedral chains of Cd-ce...

In this paper, successful one-step chemical synthesis of Co−Pt hollow spheres with adjustable composition was developed in an effort to explore new synthesis methods, simplify the synthesis procedure, and improve the synthetic efficiency. In this synthesis, a direct thermolytic reduction of platinum acetylacetonate [Pt(CH3COHCOCH3)2] and cobalt(II) acetate [Co(CH3COO)2] in refluxing ethyl glycol was explored. In the reacting mixture, an anionic surfactant sodium dodecyl sulfate (SDS) was used as the capping and structure-directing agent. These Co−Pt hollow spheres demonstrated enhanced electrocatalytic activity toward methanol oxidation in comparison with Pt nanoparticles, which is crucial for anode electrocatalysis in DMFCs.

We present a new method for predicting the thermodynamics of thermal degradation of charged cathode materials for rechargeable Li batteries and demonstrate it on three cathode materials, LixNiO2, LixCoO2, and LixMn2O4. The decomposition of LixNiO2 is a two-step process: the first step is a kinetically controlled exothermic conversion in which the layered structure transforms to the stable spinel structure. The second step is an endothermic decomposition of the spinel into a rocksalt phase, accompanied by the loss of oxygen. The heat generation for the overall reaction from the layered to the rocksalt structure is exothermic when x 0.5. From the calculated phase diagram, a similar mechanism is expected for LixCoO2, but the high migration barrier for Co may inhibit the layered-to-spinel transformation and lead to decomposition into LiCoO2 and Co3O4. For the stable spinel LiMn2O4, high temperature is needed to provide enough thermodynamic driving force for its endothermic deco...

A new family of quaternary mixed-framework chalcohalide semiconductors has been synthesized by conventional solid-state reactions in an intermediate temperature region of 400−430 °C. These include CdSbS2Cl (1), CdSbS2Br (2), CdBiS2Cl (3), CdBiS2Br (4), CdBiSe2Br (5), and CdBiSe2I (6). Single-crystal structure analyses of this compound series reveal two types of crystal structures depending upon the combination of chalcohalide anions, and they crystallize in an orthorhombic Pnma (type I) and monoclinic C2/m (type II) space group. Type I is adopted by two sulfochlorides, 1 and 3, and one selenobromide, 5. Type II is adopted by two sulfobromides, 2 and 4, and one selenoiodide, 6. Both structure types have slabs built of corner and edge shared Cd-centered CdQ6-xXx (Q = S, Se; X = Cl, Br, I; x = 0, 2, 4) octahedra that resemble the (110) plane of a distorted NaCl-type structure. In the type I structure, this slab contains only CdQ4X2 octahedra, while type II shows alternating CdQ6 and CdQ2X4 octahedra. In both...

Several TaS2/polymer nanocomposites prepared through the encapsulative precipitation method are described. Namely, the encapsulation of poly(ethylene oxide) (PEO), polyethylene imine (PEI), and poly(vinylpyrrolidinone) (PVP) into TaS2 was examined in detail, and the nanocomposites were characterized by a wide variety of techniques. The nanocomposites disperse in water and are easily cast into free-standing films. The flexible metallic TaS2/polymer nanocomposite films display bulk superconductivity. In addition, in this work the exfoliation properties of LixTaS2 were systematically explored, and it was found that material prepared from controlled lithiation with 0.2 equiv of LiBH4 exfoliates well in water and has high affinity for various polymers. The likely conformation of PEO molecules sandwiched between the TaS2 slabs was explored with analysis of the X-ray diffraction patterns of a highly oriented Lix(PEO)yTaS2 nanocomposite films. The one-dimensional electron density maps, obtained for Lix(PEO)yTaS2,...

α-RuCl3 is a new host for polymer intercalation using an in situ redox intercalative polymerization recaction. With the aid of ambient oxygen, aniline molecules get oxidatively polymerized by the R...