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Fe 5 Ni 4 S 8−x electrocatalysts toward HER were developed through surface reconstruction and vacancy engineering. The optimal electrocatalyst exhibited the overpotential of 107 mV@10 mA cm−2 and a small Tafel slope of 40 mV dec−1 in acidic media. [Display omitted] • The surface reconstruction in (3 1 1) facets of pentlandite exposes more active sites. • Sulfur vacancies generated at the site bridging two metal cubes can provide bimetallic catalytic sites. • Pentlandite with appropriate sulfur vacancy content exhibited high HER activity. Transition metal sulfide pentlandite, (Fe, Ni) 9 S 8 , emerges as a prominent catalyst for electrolytic hydrogen evolution reaction (HER) owing to high conductivity and stability. In order to investigate the effect of sulfur (S) vacancy content on the HER activity of (Fe, Ni) 9 S 8 for optimal HER activity, controlled levels of S vacancies need to be generated. Herein, Fe 5 Ni 4 S 8− x electrocatalysts toward HER were developed through surface reconstruction and S vacancy engineering through a simple heat treatment method. The surface reconstruction could regulate the surface structure to be more stable and lead to a higher number of exposed active sites. S vacancies provided an Fe–Ni synergistic effect to facilitate the hydrogen adsorption, further improving catalytic activity. The optimal Fe 5 Ni 4 S 8− x electrocatalyst exhibited the overpotential of 107 mV at 10 mA cm−2 in acidic media. Tafel slope and electrochemical impedance spectroscopy further demonstrate that the proposed thermal treatment to modulate the S vacancy content is a feasible approach to further accelerate the HER kinetics. This study provides valuable insights for the rational formulation of high-efficiency pentlandite electrocatalysts. [ABSTRACT FROM AUTHOR]

Development of efficient electrocatalysts requires construction of catalytic surfaces with moderate H adsorption energy. Here, we address this challenge by Br-induced formation of P-poor defective nickel phosphide and show that the H adsorption energy can be optimized by regulating the vacancy concentration. We show that when such defective Ni 12 P 5−x Br x nanoparticles are distributed on the surface of Ni 2 P nanosheets (Ni 12 P 5−x Br x /Ni 2 P NS), excellent catalytic activity for water splitting is obtained in alkaline media. Density functional theory computations revealed that Br doping induce the formation of a P-poor nickel phosphide with vacancies, leading to an optimal H adsorption strength with a volcano-type relationship. This is the best reported for a non-precious metal phosphide at present: the overpotential for HER is 18 mV at 10 mA cm−2 and 155 mV for OER. This leads to an exceptionally low cell voltage requirement of only 1.44 V to drive overall water splitting in an alkaline electrolyzer. [Display omitted] • Br-induced nickel phosphide formation energy change achieves P-poor defective phase configuration. • Multi-level regulation of vacancy content, morphology and catalytic performance by temperature is achieved. • DFT calculations show that Ni 12 P 5−x Br x shows a volcano-type relationship related to vacancy content. [ABSTRACT FROM AUTHOR]

Dual-metal single-atom catalysts (DACs) with an intrinsic synergy and multiple coordination structures are flourishing for oxygen reduction reaction (ORR), on the basis of optimization and regulation of the electron configuration for active centers. Herein, a two-step strategy consisting of cavity confinement and post-adsorption is developed to prepare a nitrogen-doped carbon catalyst co-supported by high-density ZnN 4 and CoN 4 sites (denoted as ZnCo-NC-II) through metal-organic framework (MOF) engineering. Structural characterization incorporated with density functional theory (DFT) calculation demonstrates that electrons are transferred from Zn (donors) to nearby Co (acceptors) through the conjugated graphene π-bond. The optimized Co d -band center achieves a moderate adsorption strength between O 2 and CoN 4 active sites. So, the rate-determining step (RDS) for the *OOH formation is accelerated. Therefore, ZnCo-NC-II exhibits a distinguished ORR activity with a half-wave potential (E 1/2) of 0.86 and 0.79 V (vs RHE) in alkaline and acid media, respectively. The zinc-air battery built with the ZnCo-NC-II catalyst shows excellent electrochemical performance for an immediate practical application. Our work is conducive to an atomic-level clarification on both the composition and design and thereof the synergistic catalytic mechanism with dual-metal sites. [Display omitted] • The atomic-level optimization and regulation enable single Zn/Co atomic couples for efficient ORR and zinc-air battery. • Zn (donors) with lower electronegativity transfers electrons to nearby Co (acceptors) through the conjugated graphene π-bond. • The electron transfer effect between the dual-metal couples optimizes the electronic structure of CoN 4 active sites, effectively reducing the adsorption strength of CoN 4 -O 2. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pyridine conjugated graphitic carbon nitride is successfully synthesized. • As-prepared catalyst exhibits superior photocatalytic hydrogen evolution. • Modulated localization of electron cloud density in as-prepared catalyst. • Narrowed bandgap and enhanced carriers' separation efficiency in as-prepared catalyst. High photogenerated carrier recombination and poor visible light response in symmetry graphitic carbon nitride are two classical problems for photocatalytic hydrogen evolution. In this work, we rationally design a novel carbon nitride (DPCN) with asymmetric embeddedness of pyridine ring. The embedded pyridine ring modulates the localization of electron cloud density, resulting in a narrowed bandgap and an enhanced carriers' separation efficiency. They are further confirmed by UV–vis spectra and femtosecond transient absorption (fs-TA) spectroscopy, whose results are consistent with DFT theoretical calculations. This DPCN catalyst shows enhanced photocatalytic hydrogen evolution rate of 180.5 μmol h−1 and the apparent quantum efficiency of 14.6 % at 420 nm, surpassing most reported g-C 3 N 4 -based photocatalysts. This work provides a new sight on designing two-dimensional photocatalysts by modulating the localization of electron cloud density through breaking topological symmetry. [ABSTRACT FROM AUTHOR]

[Display omitted] • Colorful infrared transmittance modulators are developed. • A novel asymmetric "IRPCM" FP cavity is designed. • Design principles and materials map of IRPCM are provided. • Besides GeTe, GeSe 0.75 Te 0.25 and Ge 4 Sb 0.5 Bi 0.5 Te 5 are also IRPCM candidates. • High performance of GeTe results from its small-atom composition and intrinsic-vacancy-free structure. Colorful infrared transmittance modulators (CITM) have important applications in many emerging optical fields. However, there are no rich colors in the existing infrared-transmittance modulators. The selective reflection-enhanced Fabry-Perot (FP) cavities in rich colors cannot obtain transmittance modulation performance owing to the use of metallic reflective layers. Here, we design an asymmetric FP cavity with high-optical-contrast infrared phase change materials as the reflective layer (named as "IRPCM" cavity), achieving a combination of infrared transmittance modulation and desired colors. As a proof-of-concept, our prepared IRPCM cavity composed of ZnS/GeTe not only has infrared transmittance modulation performance (66%, 3–5 μm) much greater than that of the traditional Ge 2 Sb 2 Te 5 film (38%), but also has colors. By combining theoretical calculations with experiments, we show that the high transmittance modulation performance of GeTe results from its small atomic composition and intrinsic vacancy-free structure. Based on the new insights, we propose the design principles of IRPCM and outline the materials map. The results show that besides GeTe, GeSe 0.75 Te 0.25 and Ge 4 Sb 0.5 Bi 0.5 Te 5 are also IRPCM candidates. Therefore, this study provides new IRPCMs for solving the problem of integrating colors with infrared-transmittance modulation in a thin film. [ABSTRACT FROM AUTHOR]

Synergistic functionalization of interface coagulation stimulation and liquid absorption capacity is the key to improve the hemostatic efficiency of hemostats. Herein, we prepared a graphene-ophicalcite (OPH) heterogeneous composite sponge (GOCS) by using the heterogeneous gradient composite strategy. The sponge took cross-linked graphene sponge (CGS) as the main skeleton, allowing the OPH to be controllably positioned on the surface of GOCS. The heterogeneous strategy gave full play to the advantages of the material. On the one hand, GOCS had excellent liquid absorption ability, which enriched blood cells and other coagulation components at the wound interface after contacting blood. On the other hand, the OPH at the interface obviously activated platelets and rapidly triggered coagulation cascade reactions, exhibiting fast response and feedback characteristics for coagulation signals. Under the synergistic effects, the blood clotting index value of GOCS was reduced to 33.87 ± 9.97%, which was significantly lower than those of OPH (46.33 ± 16.85%) and CGS (67.53 ± 5.35%). Importantly, GOCS rapidly stopped bleeding within 51 s in the rat femoral artery model, suggesting its great potential in the field of hemostasis. Therefore, this study provides a new idea for the design and preparation of hemostatic materials via heterogeneous strategy. [Display omitted] • Graphene/ophicalcite composite sponge (GOCS) is developed by a heterogeneous way. • Ophicalcite anchored on GOCS surface shows superior ability to activate platelet. • GOCS maximizes hemostatic effect by mimicking the process of coagulation cascade. • GOCS shows excellent hemostatic performance and stops bleeding within 51 s in vivo. [ABSTRACT FROM AUTHOR]

Optical waveguide (OWG) biosensor has attracted much attention according to the high sensitivity and resolution compared with conventional surface plasmon resonance (SPR) biosensor. Nanoporous materials are usually used as the waveguide layer for absorbing analytes into the porous structure and enhancing the sensor signal. However, this kind of waveguide layer provides poor protection to the metal film and leads to the damage of the biosensor. Ag film can provide great sensitivity in SPR sensing comparing to other metal but was rarely used because of its poor chemical stability. Fabricating high stability Ag based SPR biosensor is still a challenge. In this work we produce an OWG biosensor using a dense TiO 2 film as the waveguide layer which provides high resolution and remarkable protection to the metal film. This waveguide structure makes long time detection possible using Ag as the metal layer and is able to lead an enhancement of sensitivity comparing to the Au-based biosensor. [ABSTRACT FROM AUTHOR]

Although the control of bond structure and optical properties in hydrogenated amorphous germanium carbonitride films (a-GeC 1− x N x :H) is important for technological applications, the composition dependence of chemical bonds, especially hydrogen-containing bonds, is not yet well explored. The evolution in refractive index ( n ) and Urbach tail width ( E 0 ) remains unclear. Here, we show that nitrogen content ( C N ) exerts a significant effect on bonding structure and optical properties of a-GeC 1− x N x :H films. As C N increases, the fraction of N H increases, whereas that of C H and Ge H bonds reduces, and Ge N bonds form at expense of Ge C bonds. The replacement of carbon by nitrogen induces a substantial decrease in n from 3.0 to 2.3 because of decrease in electronic polarizability. With increasing C N , a significant increase in E 0 from 198.8 to 327.9 meV takes place. This behavior arises from decrease in dielectric coefficient ( ε ), rather than the change in the degree of disorder previously believed. The change in E 0 is proportional to the variation in 1/ ε 2 , which agrees well with hydrogen-like atom model. This study discovers that a-GeC 1− x N x :H films have the apparent tunability of n and E 0 over a wide range, which is useful in controlling the optical transmission and absorption characteristics of these films. [ABSTRACT FROM AUTHOR]

Amorphous carbon (a-C) films with various thicknesses depending on the reaction time are deposited on the surface of Ti 1.4 V 0.6 Ni alloy electrodes for Ni-MH (nickel-metal hydride) battery by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD). With the increasing deposition time, the Raman spectra show a gradually disordered sp 2 -bonding change of the films and the changing trend of sp 2 / sp 3 is obtained by X-ray photoelectron spectroscopy. The a-C film of depositing for 30 min with the thickness of 400 nm shows a favorable stability in alkaline electrolyte, the capacity is enhanced by 36.2% after 50 cycles than the bare electrode, and the charge voltage is 80 mV lower than the bare one. The a-C film with high sp 2 -bonded carbon content effectively reduces the charge transfer resistance, and as a coating layer, the dissolution of V of the alloy is also inhibited. In particular, to get a proper discharge voltage and a stable capacity simultaneously, covering completely and an appropriate thickness of the a-C film are crucial for an expected performance. [ABSTRACT FROM AUTHOR]

In the present study, the photochemical growth of silver nanoparticles under the irradiation of mixed light was examined. Monodispersed silver triangular nanoplates were synthesized by mixed light irradiation. By tuning the relative intensity of excitation wavelengths in the mixed light, the localized surface plasmon resonance (LSPR) properties of the silver nanoparticles were modulated and controlled. A cooperative effect of excitation wavelengths on regulating the growth of silver nanoparticles was outlined. [ABSTRACT FROM AUTHOR]

The designed preparation of pure and Au-loaded SnO 2 hollow multilayered nanosheets for CO detection has been realized via a rational combination of different purposeful multi-step synthetic route. The synthetic step-dependent shape and structure evolution has been investigated and the formation mechanism for the unique hollow nanosheets is also discussed. The characterized results confirm that flowerlike SnO 2 nanosheets with a polycrystalline rutile structure are assembled from hexagonal mesoporous and multilayered walls, which can further be subdivided into SnO 2 nanoparticles as structural subunits. Furthermore, gas sensors based on the as-prepared pure and Au-loaded SnO 2 have also been fabricated. The Au-loaded SnO 2 hollow nanosheets show significantly lower working temperature, faster response-recovery and improved selectivity to CO in comparison with that of pure SnO 2 . Besides structural merits including hollow and easily penetrated multilayered walls, which facilitate the transport rate and augment the adsorption quantity of gas molecule, the significant improvement of the sensing properties is also attributed to the catalytic effect of Au. [ABSTRACT FROM AUTHOR]

An examination of the effect of B- and P-doping and codoping on the electronic structure of anatase TiO2 by performing density functional theory calculations revealed the following: (i) B- or P-doping effects are similar to atomic undercoordination effects on local bond relaxation and core electron entrapment; (ii) the locally entrapped charge adds impurity levels within the band gap that could enhance the utilization of TiO2 to absorb visible light and prolong the carrier lifetime; (iii) the core electron entrapment polarizes nonbonding electrons in the upper edges of the valence and conduction bands, which reduces not only the work function but also the band gap; and (iv) work function reduction enhances the reactivity of the carriers and band gap reduction promotes visible-light absorption. These observations may shed light on effective catalyst design and synthesis. [ABSTRACT FROM AUTHOR]

A boron carbide coating was applied to diamond particles by heating the particles in a powder mixture consisting of H3BO3, B and Mg. The composition, bond state and coverage fraction of the boron carbide coating on the diamond particles were investigated. The boron carbide coating prefers to grow on the diamond (100) surface than on the diamond (111) surface. A stoichiometric B4C coating completely covered the diamond particle after maintaining the raw mixture at 1200 °C for 2 h. The contribution of the boron carbide coating to the oxidation resistance enhancement of the diamond particles was investigated. During annealing of the coated diamond in air, the priory formed B2O3, which exhibits a self-healing property, as an oxygen barrier layer, which protected the diamond from oxidation. The formation temperature of B2O3 is dependent on the amorphous boron carbide content. The coating on the diamond provided effective protection of the diamond against oxidation by heating in air at 1000 °C for 1 h. Furthermore, the presence of the boron carbide coating also contributed to the maintenance of the static compressive strength during the annealing of diamond in air. [ABSTRACT FROM AUTHOR]

Noble metal borides RuB 1.1 , RuB 2 and Ru 2 B 3 have been synthesized by mechanical alloying and high pressure sintering methods using ruthenium (Ru) and boron (B) powders as raw materials. The crystal structures of borides were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results shown that only RuB 1.1 with hexagonal crystal structure was synthesized during the ball milling process, the orthorhombic RuB 2 was synthesized under high pressure (5 GPa) and high temperature (1000 °C) conditions, while the hexagonal Ru 2 B 3 can be synthesized under 5 GPa and 1200 °C. The mechanism of synthesis for the ruthenium borides (RuB x ) are discussed in details. [ABSTRACT FROM AUTHOR]

It is a big challenge to construct proton-conductive materials for practical applications operating at high temperatures and low humidity. Herein, we propose an ionothermal strategy for the preparation of highly stable NH2-MIL-53(Al)it nanomaterials with high proton conductivity. The crystalline structure and the direct incorporation of the 1-ethyl-3-methyl-imidazolium ionic liquid within NH2-MIL-53(Al)it are identified by XRD, TG/DTA and IR techniques. The as-prepared NH2-MIL-53(Al)it exhibits a high proton conductivity of 3.0 × 10−5 S cm−1 at 80 °C and low relative humidity of ∼26%. [ABSTRACT FROM AUTHOR]

The unique flowerlike SnO 2 hollow nanosheets with multilayer walls have been successfully synthesized by a simple anneal-etching strategy based on flowerlike ZnSn(OH) 6 solid nanosheets. FESEM and TEM observations reveal that this new type of nonspherical SnO 2 hollow structure is composed of hexagonal hollow nanosheets with mesoporous and multilayered interiors, where the secondary building blocks are numerous nanoparticles. Synthetic step-related investigation demonstrates that the formation of flowerlike hollow nanosheets with mesoporous and multilayer walls are ascribed to the final well-preserved shapes of flowerlike ZnSn(OH) 6 solid template and the critical hollowing process in the last etching treatment. The well-aligned porous and multilayer walls of SnO 2 hollow nanosheets retain actual high surface area and surface accessibility, and the improved gas sensing performances can be anticipated. It is found that our SnO 2 nanostructures have a response of 18.3–50 ppm acetone at the optimal working temperature of 300 °C, and the response time and recovery time are within 0.9 and 5.8 s, respectively. [ABSTRACT FROM AUTHOR]

Although vacancies exist commonly in nonstoichiometric transition metal nitrides, their roles on structure and properties are not yet well explored. We show that in rocksalt hafnium nitride films creation of nitrogen and hafnium vacancies leads to an asymmetrical lattice contraction and distortion from cubic to rhombohedral structure owing to the presence of strong texture and compressive stress, and also causes decrease in hardness because of reduction in bulk modulus and decrease in electrical conductivity due to reduction in electron relaxation time. This new insight into vacancy-induced “negative effect” is demonstrated through good matches between our experiments and theoretical calculations. [ABSTRACT FROM AUTHOR]

The interplay of superconductivity and magnetism is a subject of ongoing interest, stimulated most recently by the discovery of Fe-based superconductivity and the recognition that spin-fluctuations near a magnetic quantum critical point may provide an explanation for the superconductivity and the order parameter. Here we investigate magnetism in the Na filled Fe-based skutterudites using first principles calculations. NaFe4Sb12 is a known ferromagnet near a quantum critical point. We find a ferromagnetic metallic state for this compound driven by a Stoner type instability, consistent with prior work. In accord with prior work, the magnetization is overestimated, as expected for a material near an itinerant ferromagnetic quantum critical point. NaFe4P12 also shows a ferromagnetic instability at the density functional level, but this instability is much weaker than that of NaFe4Sb12, possibly placing it on the paramagnetic side of the quantum critical point. NaFe4As12 shows intermediate behavior. We also present results for skutterudite FeSb3, which is a metastable phase that has been reported in thin film form. [ABSTRACT FROM AUTHOR]

Low hardness and optical gap of amorphous germanium carbon films limit their applications as antireflective and protective coatings (APC). This study reports that incorporating suitable amount of nitrogen into the films during the sputtering process effectively enhances the hardness and optical gap without significant sacrifice of the original far-infrared transmission. Our first-principle calculations show that the observed hardness and optical gap enhancement arises from transition from weak Ge–C to strong Ge–N bonds with nitrogen incorporation. These nitrogen-incorporated germanium carbon films are good as APC on high-speed far-infrared windows. [ABSTRACT FROM AUTHOR]

A stoichiometry-driven phase transition from rocksalt to “nitrogen-rich” structure exists in group-IVB transition metal nitride films. As this phase transition is critical in controlling the film properties it has attracted numerous studies. However, researchers are still divided with regard to the structural identity of this “nitrogen-rich” phase, not to mention detailed exploration of the phase transition mechanisms. In this study, we confirmed that the “nitrogen-rich” phase in hafnium nitride (HfN x ) films had a cubic Th 3 P 4 structure of space group symmetry of I- 43 d (220), namely c -Hf 3 N 4 . The confirmation was obtained by combining the first-principle calculations with a series of experiments: Selected Area Electron Diffraction, High Resolution Transmission Electron Microscopy, Raman, Gracing Incident X-ray Diffraction and X-ray Photoelectron Spectroscopy. The mechanisms of the phase transition were elucidated through calculations on enthalpy of formation ( EOF ). The experimental results agree well with the theoretical calculations. We conclude that with increasing nitrogen, phase transition takes place from rocksalt ( δ -HfN) to c -Hf 3 N 4 through three stages of structural evolution: δ -HfN (containing Hf vacancies) → mixture of ( δ -HfN + c -Hf 3 N 4 ) → c -Hf 3 N 4 . The driving force of the phase transition is energy minimization. The three stages of structural evolution are explained by comparing the EOF of the δ -HfN and c -Hf 3 N 4 phases. As the phase transition takes place, the hafnium nitride film morphs from a conductive and opaque metal into an insulating and transparent semiconductor. [ABSTRACT FROM AUTHOR]

We present recent progress in understanding the anomalous behavior of water ice under mechanical compression, thermal excitation, and molecular undercoordination (with fewer than four nearest neighbors in the bulk) from the perspective of hydrogen (O:H O) bond cooperative relaxation. We modestly claim the resolution of upwards of ten best known puzzles. Extending the Ice Rule suggests a tetrahedral block that contains two H 2 O molecules and four O:H O bonds. This block unifies the density-geometry-size-separation of molecules packing in water ice. This extension also clarifies the flexible and polarizable O:H O bond that performs like a pair of asymmetric, coupled, H-bridged oscillators with short-range interactions and memory as well as extreme recoverability. Coulomb repulsion between electron pairs on adjacent oxygen atoms and the disparity between the O:H and the H O segmental interactions relax the O:H O bond length and energy cooperatively under stimulation. A Lagrangian solution has enabled mapping of the potential paths for the O:H O bond at relaxation. The H O bond relaxation shifts the melting point, O 1s binding energy, and high-frequency phonon frequency whereas the O:H relaxation dominates polarization, viscoelasticity, and the O:H dissociation energy. The developed strategies have enabled clarification of origins of the following observations: (i) pressure-induced proton centralization, phase transition-temperature depression and ice regelation; (ii) thermally induced four-region oscillation of the mass density and the phonon frequency over the full temperature range; and (iii) molecular-undercoordination-induced supersolidity that is elastic, hydrophobic, thermally stable, with ultra-low density. The supersolid skin is responsible for the slipperiness of ice, the hydrophobicity and toughness of water skin, and the bi-phase structure of nanodroplets and nanobubbles. Molecular undercoordination mediates the O:H and H O bond Debye temperatures and disperses the quasi-solid phase boundary, resulting in freezing point depression and melting point elevation. O:H O bond memory and water-skin supersolidity ensures a solution to the Mpemba paradox — hot water freezes faster than its cold. These understandings will pave the way toward unveiling anomalous behavior of H 2 O interacting with other species such as salts, acids and proteins, and excitation of H 2 O by other stimuli such as electrical and magnetic fields. [ABSTRACT FROM AUTHOR]

Although point defects are found to exist commonly in non-stoichiometric group-IVB transition metal nitrides, the identification of primary point defects still causes some disagreement. The formation mechanism and influence of primary point defects on electronic structures are not yet well explored. This study finds that the types and formation mechanism of primary point defects in rocksalt hafnium nitride (δ-HfN x ) films can be identified by a combination of first-principles calculations and grazing incidence X-ray diffraction, Raman and high-resolution transmission electron microscopy experiments. It is shown that the primary point defects in sub- and over-stoichiometric δ-HfN x films are N and Hf vacancies, respectively, which arise preferentially because they are thermodynamically more stable than other types of point defects, such as interstitials and antisites, because they have much lower formation energy and equilibrium formation enthalpy. Furthermore, it is found that the formation of N and Hf vacancies have an important role in changing electronic structures. N vacancies act as donor-like defects and can add extra free electrons to the conduction band at a rate of an electron per N vacancy, while Hf vacancies serve as acceptor-like defects and efficiently reduce free electrons at a rate of two electrons per Hf vacancy. Additionally, the formation of N vacancies can induce two new interband absorption bands centered at ∼0.81 and ∼2.27 eV, while the incorporation of Hf vacancies create an additional interband absorption band at ∼3.75 eV. These new insights are demonstrated by good agreement between calculations and experiments. [ABSTRACT FROM AUTHOR]

Abstract: The binding of DNA with graphene oxide (GO) is important for applications in disease diagnosis, genetic screening, and drug discovery. The standard assay methods are mainly limited to indirect observation via fluorescence labeling. Here we report the use of surface plasmon resonance for direct sensing of DNA/GO binding. We show that this can be used for ultra-sensitive detection of single-stranded DNA (ssDNA). Furthermore, the results provide a more direct probe of DNA/GO binding abilities and confirm that hydrogen bonding plays a key role in the interaction between GO and ssDNA. This enables to a novel biosensor for highly sensitive and selective detection of ssDNA based on indirect competitive inhibition assay (ICIA). We report development of such a sensor with a linear dynamic range of 10−14–10−6 M, a detection limit of 10fM and a high level of stability during repeated regeneration. [Copyright &y& Elsevier]

Photocatalytic Hydrogen Evolution In article number 2200298 Xiaoqiang Cui and co‐workers report a novel anatase‐TiO2/H‐rutile‐TiO2 heterophase homojunction with near optimum energy band alignment. The resulting catalyst exhibits an excellent photocatalytic hydrogen evolution rate of 29.63 mmol g−1 h−1 and an outstanding apparent quantum efficiency of 45.6%. The significant improvement is ascribed to near perfect lattice matching in combination with the rapid separation and transfer of photogenerated carriers. [ABSTRACT FROM AUTHOR]

Apparent quantum efficiency, energy bands, heterophase homojunction, hydrogen evolution, photocatalysts Keywords: apparent quantum efficiency; energy bands; heterophase homojunction; hydrogen evolution; photocatalysts EN apparent quantum efficiency energy bands heterophase homojunction hydrogen evolution photocatalysts 1 1 1 04/29/22 20220427 NES 220427 B Photocatalytic Hydrogen Evolution b In article number 2200298 Xiaoqiang Cui and co-workers report a novel anatase-TiO SB 2 sb /H-rutile-TiO SB 2 sb heterophase homojunction with near optimum energy band alignment. Favorable Energy Band Alignment of TiO2 Anatase/Rutile Heterophase Homojunctions Yields Photocatalytic Hydrogen Evolution with Quantum Efficiency Exceeding 45.6% (Adv. [Extracted from the article]

Highlights: [•] Ni(OH)2/vertically oriented graphene nanosheets (V-GNs) was prepared. [•] Ni(OH)2/V-GNs had enhanced specific capacitance, cycling reversibility and stability. [•] Performance of Ni(OH)2/GNs/NF-AC asymmetric supercapacitor was studied. [ABSTRACT FROM AUTHOR]

Abstract: Transition metal is usually required for obtaining N-doped carbon (dN-C) catalysts toward oxygen reduction reaction, leading to an intense debate on whether the active sites in dN-C correlate to transition metal. Here, we report that metal-free amorphous dN-C was synthesized using simple one-step magnetron sputtering at relatively low temperature. The chemical bonding states of N atoms, which play a key role in optimizing the electrocatalytic activity, can be tuned by adjusting deposition temperature. The metal-free dN-C with high pyridinic N content exhibits high electrocatalytic activity, and its stability and methanol tolerance are much better than commercial Pt/C catalyst. [Copyright &y& Elsevier]

We report on a new and facile method for the preparation of well-dispersed gold-palladium (AuPd) flower-shaped nanostructures on sheets of graphene oxide (GO). Transmission electron microscopy and high angle annular dark field STEM were used to characterize the morphology and composition of the new nanohybrids. The AuPd/GO composites display high electrocatalytic activity for the oxidation of ethanol in strongly alkaline medium as examined by cyclic voltammetry and chronoamperometry. Both the current density (13.16 mA · cm at a working potential of −0.12 V) and the long-time stability are superior to a commercial Pd-on-carbon catalyst which is attributed to the cooperative action of the catalytic activities of Au and Pd, and the good dispersion of the alloy on the nanosheets. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: We present an approach for distillation of the coordination-resolved electronic binding energy and bond relaxation dynamics, which has enabled clarification of the catalytic nature of under- and hetero-coordinated atoms. It is classified that Pt adatoms and CuPd alloy serve as acceptor-type catalysts because of the bond-order-deficiency induced quantum entrapment while Rh adatoms and AgPd alloy serve as donor-type catalysts because of the polarization of the conduction electrons of the adatoms by the densely, locally entrapped core electrons. This technique also enables the distillation of the polarized electronic states of graphite point defects and the entrapped states of the monolayer skin of graphite, which may serve, respectively, donor- and acceptor-type catalyst. The developed approach complements scanning tunneling microscopy/spectroscopy and photoelectron spectroscopy for the atomistic, local, and quantitative information of bond and electronic relaxation dynamics. [Copyright &y& Elsevier]

ZnSnO3 hollow microspheres with a hierarchical structure composed of small nanorods as building blocks are synthesized by a facile one-pot hydrothermal method at 160°C. The individual hierarchical ZnSnO3 microsphere ranges from 600 to 900nm in diameter. The time-dependent hollowing evolution of ZnSnO3 microspheres reveals that the preferential formation of solid ZnSnO3 microspheres and the subsequent dissolution of the interiors to form hollow architectures are performed via Ostwald ripening. Moreover, ZnSnO3 spheres with hollow interiors and permeable surfaces are exploited as gas sensors, exhibiting improved sensing performances to ethanol. The response-recovery times of sensor based on these ZnSnO3 hollow microspheres are 0.9 and 2.2s when the sensor is exposed in ethanol at the optimal operating temperature of 270°C. The significant decrease in response-recovery times are attributed not only to the surface accessibility obtained by the hierarchical hollow architectures, but also to these rodlike building blocks with ultra-thin diameters. [ABSTRACT FROM AUTHOR]

Abstract: NbN/AlN nano-multilayer films with AlN layer thickness (l AlN) ranging from 2.2 to 12.2nm have been deposited on Si(100) substrate by reactive magnetron sputtering in Ar/N2 mixtures. The l AlN dependent structural and mechanical properties for resulting NbN/AlN multilayers have been evaluated by means of low-angle X-ray reflectivity, X-ray diffraction, transmission electron microscope, pole figure measurements and nanoindentation tests. The finding is that at small l AlN both hexagonal wurtzite-AlN(0002) and face-centered cubic (fcc) AlN(111) are coherent with the fcc NbN(111), and the increase of l AlN can promote coherent growth of fcc-NbN(111)/w-AlN(0002) due to minimization of total energy and formation of a strong NbN(111)/AlN(0002) fiber texture. The hardness of all NbN/AlN multilayers lies in between 32.7 and 37.5GPa with increasing l AlN from 2.2 to 12.2nm, which is obviously higher than that calculated by using a simple rule of mixture, showing that the remarkable hardness enhancement implements at a wide range of l AlN from 2.2 to 12.2nm for NbN/AlN multilayer system. The high-hardness value in a wide range of l AlN can be mainly attributed to Koehler mechanism and structural barriers (fcc/hexagonal) to dislocation motion between NbN and AlN layers. [Copyright &y& Elsevier]

Highlights: [•] The coherent relationship of forms in multilayer. [•] The remarkable hardness enhancement implements at a wide range of modulation periodicity. [•] Good wear property appears in multilayers with small modulation periodicity. [ABSTRACT FROM AUTHOR]

Abstract: Nanoscaled or porous silicon (p-Si) with and without surface passivation exhibits unusually tunable properties that its parent bulk does never show. Such property tunability amplifies the applicability of Si in the concurrent and upcoming technologies. However, consistent understanding of the fundamental nature of nanoscaled Si remains a high challenge. This article aims to address the recent progress in this regard with focus on reconciling the tunable dielectric, electronic, phononic, and photonic properties of p-Si in terms of skin dominance. We show that the skin-depth bond contraction, local quantum entrapment, and electron localization is responsible for the size-induced property tunability. The shorter and stronger bonds between undercoordinated skin atoms result in the local densification and quantum entrapment of the binding energy and the bonding electrons, which in turn polarizes the dangling bond electrons. Such local entrapment modifies the Hamiltonian and associated properties such as the band gap, core level shift, Stokes shift (electron–phonon interaction), phonon and dielectric relaxation. Therefore, given the known trend of one property change, one is expected to be able to predict the variation of the rest based on the notations of the bond order–length–strength correlation and local bond average approach (BOLS-LBA). Furthermore, skin bond reformation due to Al, Cu, and Ti metallization and O and F passivation adds another freedom to enhance or attenuate the size effect. The developed formulations, spectral analytical methods, and importantly, the established database and knowledge could be of use in engineering p-Si and beyond for desired functions. [Copyright &y& Elsevier]

Abstract: Flower-shape palladium nanostructures have been synthesized on the surface of graphene oxide by a simple effective method in the absence of any reducing chemical reagent. Atomic force microscopy (AFM), and Fourier transform infrared spectra (FT-IR) were used to characterize GO. The flower-shape palladium/Graphene oxide (FS-Pd/GO) nanocomposites are characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD). As-prepared FS-Pd/GO nanocomposites exhibited excellent performance on the electrocatalytic oxygen reduction reaction (ORR) and the glucose oxidation reaction. This method may open a general approach for preparing metal nanostructures on GO sheets for applications in fuel cells, biosensing and other fields. [Copyright &y& Elsevier]

Abstract: Novel iridium nitrides (IrN x ) have been synthesized from a double decomposition reaction between IrCl3 and Li3N powders under high pressure (5GPa) and high temperature (1273K) conditions. X-ray diffraction and Raman spectra analysis reveals that the as-synthesized IrN x have a cubic crystal structure. The lattice constants of IrN x are 4.06Å. The x-ray photoelectron spectrum indicates the N content (x) in IrN x is ∼0.3. The first-principles calculations further suggest that iridium nitride is face-centered cubic structure, which has not ever been reported experimentally. Such structure is mechanical stable even under 10GPa and 1273K conditions. [Copyright &y& Elsevier]

Highlights: [•] Co(OH)2/graphene and Co(OH)2/amorphous carbon were prepared. [•] Co(OH)2/graphene reveals a high cycling stability even at a high current density. [•] Co(OH)2/amorphous carbon exhibits a high specific capacitance. [•] Influence of carbon on pseudocapacitive behaviors of Co(OH)2 has been studied. [ABSTRACT FROM AUTHOR]

[Display omitted] • Intramolecular heterostructured carbon nitride is successfully synthesized. • The as-prepared sample exhibits superior photocatalytic hydrogen production. • Rapid separation and transfer of photogenerated carriers in as-prepared sample. • The addition of salt mixture regulates the localized electronic structure. Efficient separation and transfer of photogenerated carriers is vital for efficient photocatalytic hydrogen evolution. We report development of a new type of intramolecular heterostructure graphitic carbon nitride with heptazine-triazine (CN-HT) by use of a one-step thermal polymerization method. This intramolecular heterostructure changes the electronic structure to promote charge transfer and enhances the adsorption of H*. The as-prepared CN-HT exhibits superior photocatalytic hydrogen evolution of 88.29 μmol/h, which is 14.2 times that of pristine CN. The apparent quantum yield is 10.1% at 400 nm and 9.6% at 450 nm. The efficient separation and transfer of photogenerated carriers as well as the expanded visible light absorption in this intramolecular CN heterostructure contribute to the efficient utilization of photogenerated carriers, thus enhancing the photocatalytic hydrogen evolution. [ABSTRACT FROM AUTHOR]

Metal halide perovskite nanocrystals (NCs) attract much attention for light-emitting applications due to their exceptional optical properties. More recently, perovskite NCs have begun to be considered a promising material for nonlinear optical applications. Numerous strategies have recently been developed to improve the properties of metal halide perovskite NCs. Among them, B-site doping is one of the most promising ways to enhance their brightness and stability. However, there is a lack of study of the influence of B-site doping on the nonlinear optical properties of inorganic perovskite NCs. Here, we demonstrate that Cd2+ doping simultaneously improves both the linear (higher photoluminescence quantum yield, larger exciton binding energy, reduced trap states density, and faster radiative recombination) and nonlinear (higher two- and three-photon absorption cross-sections) optical properties of CsPbBr3 NCs. Cd2+ doping results in a two-photon absorption cross-section, reaching 2.6 × 106 Goeppert-Mayer (GM), which is among the highest reported for CsPbBr3 NCs. [ABSTRACT FROM AUTHOR]

Graphene oxide nanosheet is an ideal platform to capture nanoparticles for highly efficient catalysis, electrochemical sensing and biosensing. In this work, we have described a simple synthesis method for preparation graphene oxide- nanohybrid. nanodots with an average size of 1.6 nm uniformly dispersed on the surface of graphene oxide. The well-defined nanostructure has been characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The nanohybrid also exhibits enhanced catalytic activity toward the reduction of 4-nitrophenol by . Comparing with pure nanodots and graphene oxide, graphene oxide- nanohybrid shows the highest catalytic activity. This approach not only suggests a wide potential application of graphene oxide nanosheet as a host material for supporting a variety of nanoparticles, but also provides a new approach for the fabrication of graphene-based nanohybrids with multiple physical and chemical properties. Graphene oxide-Au nanohybrid has been prepared to enhance the catalytic activity toward the reduction of 4-nitrophenol. [ABSTRACT FROM AUTHOR]

Graphene is deposited on polycrystalline Co film by radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD), and the effect of deposition time on the crystallinity of graphene, such as graphitic degree and in-plane crystallite size, is explored. The findings are that graphene can be obtained on polycrystalline Co film for only 15 s, suggesting that a direct growth mechanism plays an important role in the formation of graphene. The first-principles density functional theory (DFT) results also reveal that the graphene is more easily formed on Co via a surface direct growth mechanism than that via a precipitation mechanism. Our studies are critical in guiding the graphene growth process as we try to achieve the highest quality graphene for electronic devices. [ABSTRACT FROM AUTHOR]

Abstract: A convenient and efficient preparation method for separation graphene oxide with well-defined size distribution is developed using a centrifugation technique. The graded profile of graphene oxide nanosheets with narrow size distribution is effectively controlled by varying the centrifugation speed. The results show that the oxygen content of graphene oxide is highly dependent on their size distribution. Graphene oxide nanosheet with large size shows a red-shift in UV–vis absorption spectra, compared to graphene oxide with small size. This phenomenon is interpretation by a density functional theory calculation. The present work will provide a simple method to prepare graphene oxide nanosheets with controllable size distribution and C/O ratio, which will be valuable for the functionalization of graphene-based hybrids and the fabrication of graphene nano-devices. [Copyright &y& Elsevier]

Abstract: The ZrN/SiNx double-layers with different density of SiNx layers, which was controlled by applying different substrate bias for depositing SiNx layers, were synthesized for investigating the interfacial electronic structure. Results indicated that the interfacial electrostatic polarization existed as the ZrN and SiNx bond with each other to form a heterojunction, since the electrons donated from ZrN layer to SiNx layer. Moreover, the degree of polarization was affected by the density of SiNx layer. The corresponding ZrN/SiNx multi-layers were deposited for studying the correlation between interfacial electronic structure and mechanical properties. The results of hardness test implied that the interfacial electrostatic polarization would enhance the hardness to a certain extent. [Copyright &y& Elsevier]

Abstract: We present an approach for quantifying the heterogeneous interface bond energy using X-ray photoelectron spectroscopy (XPS). Firstly, from analyzing the XPS core-level shift of the elemental surfaces we obtained the energy levels of an isolated atom and their bulk shifts of the constituent elements for reference; then we measured the energy shifts of the specific energy levels upon interface alloy formation. Subtracting the referential spectrum from that collected from the alloy, we can distil the interface effect on the binding energy. Calibrated based on the energy levels and their bulk shifts derived from elemental surfaces, we can derive the bond energy, energy density, atomic cohesive energy, and free energy at the interface region. This approach has enabled us to clarify the dominance of quantum entrapment at CuPd interface and the dominance of polarization at AgPd and BeW interfaces, as the origin of interface energy change. Developed approach not only enhances the power of XPS but also enables the quantification of the interface energy at the atomic scale that has been an issue of long challenge. [Copyright &y& Elsevier]

Large-area single- or multilayer graphene of high quality is synthesized on Ni films by radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) at a relatively low temperature (650°C). In the deposition process, a trace amount of CH gas (2-8 sccm (sccm denotes standard cubic centimeter per minute at STP)) is introduced into the PECVD chamber and only a short deposition time (30-60 s) is used. Single- or multilayer graphene is obtained because carbon atoms from the discharging CH diffuse into the Ni film and then segregate out at its surface. The layer number of the obtained graphene increases when the deposition time or CH gas flow rate is increased. This investigation shows that PECVD is a simple, low-cost, and effective technique to synthesize large-area single- or multilayer graphene, which has potential for application as electronic devices. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we have developed a simple and green method for one-pot synthesis of ultrathin gold nanocrystals attached to graphene through photo irradiation. High-yield ultrathin Au nanocrystals are distributed on the reduced graphene oxide, immediately followed by the deoxygenation of graphene oxide in the absence of chemical reductants and surfactants. The procedure has been thoroughly completed and the products have been analyzed by transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), etc. The results show that both graphene oxide and photo irradiation play essential roles in the formation of ultrathin Au nanocrystals. The nanohybrids also display excellent electro-catalytical performance to methanol oxidation. This study not only has potential in the applications of bio-sensing and fuel cells, but also provides new procedures for the preparation of metal/graphene nanomaterials. [Copyright &y& Elsevier]

The graphene/carbon nanotube hybrid was designed and implemented by a deoxygenation process for direct electron transfer of glucose oxidase and glucose biosensor. The procedure was analyzed by transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectra, etc. The strategy of structurally engineering one-dimensional carbon nanotube (CNT) and two-dimensional graphene oxide (GO) presented three benefits: (a) a deoxygenation process between GO and acid-CNT was introduced under strongly alkaline condition; (b) GO prevented the irreversible integration of CNT; and (c) CNT hindered the restacking of GO. The RGO interacted with CNT through the van der Waals forces and π-π stacking interaction. The three-dimensional hybrid not only had a high surface area, but also exhibited a good electronic conductivity. A direct electrochemistry of glucose oxidase was obtained on the nanohybrid modified electrode which showed good response for glucose sensing. This study would provide a facile and green method for the preparation of nanohybrid for a wide range of applications including biosensing, super capacitor, and transparent electrode. [ABSTRACT FROM AUTHOR]

Abstract: A microstructure sensor based on hierarchically porous ZnO nanosheet (NS) thin films has been achieved by using a facile two-step solution phase method. The transparent ZnO seed-layer covered on both the conducting electrodes and the insulating SiO2 spacer regions acts as lattice-matched template, on which the assembly of ZnO NS thin films has been subsequently completed via a facile solvothermal process. The phase purity, morphology, and structure of the as-prepared NSs are investigated, and the results reveal that ZnO NSs, grown vertically on the substrate, exhibit hierarchically porous nanostructure with subunits of nanoparticles. The gas-sensing properties exhibit not only high response to CO with the response time of 25s, but also low cross response to common interference gases at the operating temperature of 300°C. [Copyright &y& Elsevier]

Graphite nanosheets have been grown on Ni foam by radio-frequency plasma-enhanced chemical vapor deposition, which are used as substrates for electrodepositon of Ni(OH)2 with a porous and 3D nanostructure. The Ni foam/graphite nanosheets/Ni(OH)2 electrode has a high specific capacitance of 1667 F g−1 and the specific capacitance can maintain 93.3% after 700 cycles at the current density of 60 A g−1 in 1 M KOH. [ABSTRACT FROM AUTHOR]

Vertically aligned graphene nanosheets have been synthesized by radio-frequency plasma-enhanced chemical vapor deposition on nickel-foam current collectors and that have been used as substrates for cathodic electrodeposition of cobalt hydroxide nanosheets in Co(NO 3 ) 2 aqueous solution. Raman spectrum exhibits that high-quality graphene nanosheets have been synthesized. The composites have been characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry and galvanostatic charge/discharge. It indicates that hexagonal Co(OH) 2 has a network microstructure, consisting of interlaced sheets with the thickness of 12 nm coated on the graphene nanosheets. The binder-free nano-electrode exhibits excellent pseudocapacitive behavior with pseudocapacitances of 693.8 and 506.2 Fg −1 at current density of 2 and 32 Ag −1 , respectively, in a potential range of −0.1–0.45 V. The capacitance can retain about 91.9% after 3000 charge–discharge cycles at 40 Ag −1 , which is higher than that of Co(OH) 2 /Ni foam (after 2000 cycles, 75.5% of initial capacitance remains). The introduction of graphene between Co(OH) 2 and Ni foam demonstrates an enhancement of electrochemical stability of the nano-electrodes. [ABSTRACT FROM AUTHOR]

Abstract: Vertically aligned graphene nanosheets have been synthesized by radio-frequency plasma-enhanced chemical vapor deposition on nickel-foam current collectors and that have been used as substrates for cathodic electrodeposition of cobalt hydroxide nanosheets in Co(NO3)2 aqueous solution. Raman spectrum exhibits that high-quality graphene nanosheets have been synthesized. The composites have been characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry and galvanostatic charge/discharge. It indicates that hexagonal Co(OH)2 has a network microstructure, consisting of interlaced sheets with the thickness of 12 nm coated on the graphene nanosheets. The binder-free nano-electrode exhibits excellent pseudocapacitive behavior with pseudocapacitances of 693.8 and 506.2 Fg−1 at current density of 2 and 32 Ag−1, respectively, in a potential range of −0.1–0.45 V. The capacitance can retain about 91.9% after 3000 charge–discharge cycles at 40 Ag−1, which is higher than that of Co(OH)2/Ni foam (after 2000 cycles, 75.5% of initial capacitance remains). The introduction of graphene between Co(OH)2 and Ni foam demonstrates an enhancement of electrochemical stability of the nano-electrodes. [Copyright &y& Elsevier]