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Functional materials show various highly demanded performances originating from intrinsic features related to degrees of freedom in a lattice framework. Presently, deep physical or chemical insights of quantum materials stimulate researchers to clarify multiscale processes within both materials and devices, which may be understood as functional materials that possess energy origin beyond electron contribution. It is of great significance for the design of functional materials to understand the sources of properties of functional materials from the perspective of multi degrees of freedom via multiscale research methods. This short review illustrates the importance and explores the energy source of functional materials from multiple degrees of freedom perspectives. Moreover, we analyzed the multiple degrees of freedom within lithium niobate single crystals to clarify their multiscale features. This short review may, in some cases, provide a perspective for enhancing research scopes of functional materials and recommending some methodologies from multiple degrees of freedom perspectives. A multiscale view at lithium niobate, ranging from Li+, Nb5+ and O2− ions and their chemical bonding features, domain engineering, as well as the regulated frame with LiO 6 and NbO 6 octahedral stacking. Crystallographic structure clarifies lattice freedom order parameter, demonstrating domain kinetics and phase transition from ferro-to nonferro-state, Jahn-Teller effect, valence electron orbital hybridization, defects causing the local symmetry broken, etc. [Display omitted] • Functional materials research follows their multiscale origin and the perspective of multiple degrees of freedom. • We analyzed the degrees of freedom and coupling effects within the crystallographic structure of lithium niobate. • Studying the quantum effects of lithium niobate is to clarify the quantum source of the macro function of lithium niobate. [ABSTRACT FROM AUTHOR]

Ever-increasing global energy consumption has increased aggregate demand on electrochemical energy storage devices with high energy density. Over the past few decades, manganese oxides have attracted wide attention due to their abundant reserves, low cost, environmental friendliness, and high theoretical capacity. However, most reported manganese-based materials have exhibited capacity far below the theoretical capacity, which was only on the basis of Mn3+/Mn4+ couple. The rich chemistry of manganese enables it to exist in various valence states, such as Mn0, Mn2+, Mn3+, Mn4+, and Mn7+, providing great opportunity for discovering new manganese-based electrode systems. Herein, we formed a Mn2+/Mn4+ couple from a manganese-based colloidal system with rare earth (RE) modification, which was formed in-situ on nickel (Ni) foam in KOH electrolyte under an electric field assistance. The Mn-based colloidal electrode, with Mn:Ce mass ratio of 1:0.5, achieved a high specific capacitance of 2985 F g–1 at 3 A g–1, which was higher than the theoretical capacity of 2193 F g–1 on the basis of the Mn3+/Mn4+ couple. After the addition of Ce3+, the prepared sample exhibited improved rate capability performance. Our manganese-based colloidal electrode with RE modification delivered a high specific capacitance of 1223 F g–1 at 20 A g–1, with 54.5% retention of 2243 F g–1 at 3 A g–1 at Mn:Ce mass ratio of 1:0.05. Colloidal electrode systems involving Mn-based colloids are a novel way to engineer the electrochemical performance of inorganic materials. [ABSTRACT FROM AUTHOR]

Novel electrode materials with desired specific capacitances are needed for supercapacitors. Rare-earth (RE)-based materials are fascinating in the field of catalysis and energy. Herein, a series of hydroxides including La, Ce, Pr and Nd was synthesized via in situ precipitation. Interestingly, only Ce(OH)3 showed a redox peak in both positive and negative ranges. The other RE hydroxides exhibited a redox peak only in the positive range. Therefore, in order to certify that Ce(OH)3 can be used as a negative electrode, symmetrical supercapacitors consisting of Ce(OH)3 as both positive and negative electrodes were assembled, and showed a voltage window of 1.3 V. Moreover, asymmetrical supercapacitors were successfully fabricated, in which the positive electrode was composed of La(OH)3, Pr(OH)3 or Nd(OH)3. These results may pave the way to novel negative electrode materials. [ABSTRACT FROM AUTHOR]

Manganese oxides have attracted wide attention as promising electrode materials for high-energy density supercapacitors. However, the electrochemical performance of the manganese oxide materials deteriorates considerably with the increase in mass loading due to their moderate electronic and ionic conductivities. This phenomenon leads to low areal capacitance, which limits the practical application of these materials. Herein, we perform a potentiostatic electrodeposition of manganese oxides with Ce as rare earth (RE) modification on a nickel (Ni) foam substrate to achieve high areal capacitance. Under optimum conditions, manganese oxide nanosheets are axially grown on Ni foam to form a hierarchically porous network nanostructure, which ensures facile ionic and electric transport. The Ce-modified manganese oxide with the Mn:Ce molar ratio of 1:0.1 yields an outstanding areal capacitance of 3.67 F cm–2 at 2 mA cm–2 and a good rate capability compared with the capacitance of 2.59 F cm–2 at 2 mA cm–2 of pure manganese oxide without the addition of Ce. This result verifies the importance of Ce modification to manganese oxides. Our results suggest the important role played by the RE element Ce in enhancing the electrochemical performance of high areal capacitance manganese oxide electrodes, which is essential to bringing them one step toward further practical applications. [ABSTRACT FROM AUTHOR]

Multiscale rare earth crystal materials hold great promise for a wide range of applications, including bioimaging diagnosis, therapy, lighting, lasers, motors, and security. Rare earth crystal materials exhibit multiscale characteristics, which originate from the trans-scale process from the microscopic atomic/molecular scale to macroscopic aggregates with particular structures, geometries, sizes, and weights. In this perspective, both thermodynamic and kinetic discussions on rare earth crystal materials suggest that chemical bonding between clusters at the interface can provide an effective approach to solve the trans-scale problem. The fundamental aspects of multisize and multiweight effects of rare earth crystal materials have also been clarified. The sizes of rare earth crystal materials are determined by thermodynamic controls because each individual monosize presents its own surface and interface geometry, and its symmetry reflects the corresponding energy state. The weight of rare earth crystal materials depends on kinetic controls, including the initial concentrations of the reactants, the reaction order, the activation energy, and the reaction rate coefficient. The only method to obtain rare earth materials with different magnitudes of weight is to scale up the reactor. In order to obtain large-weight monosized rare earth materials, a variety of virtual and uniform reaction mono-regimes have been designed by numeric calculations and created by gradual amplification of experiments. Looking ahead, multidisciplinary efforts will be required to decipher the complexity of multiscale rare earth crystal materials. [ABSTRACT FROM AUTHOR]

Large-sized crystals are fundamental materials in many fields such as semiconductors, communication, military, and radiation detection. However, preparing large-sized and high-quality single crystals for high technology demands is still very difficult. Theory is an important part of crystal growth research. In this review, we briefly summarize the crystal growth models and propose the research directions for the future to break through the preparation of large crystals. In terms of application, chemical bonding theory is currently an effective model for the growth of large-sized crystals. In the future, three aspects, such as utilizing artificial intelligence technology to obtain parameters that accurately describe system properties, establishing cross-scale simulation methods, and calculating interface positions accurately, may be the keys to promote the development of large-sized crystal preparation. [ABSTRACT FROM AUTHOR]

The development of cost- and time-effective methods to synthesize graphene materials is very urgent in order to promote its large-scale application in electrochemical energy storage devices. Herein, graphene materials were synthesized by the electrochemical exfoliation (electrochemical oxidation) of graphite-clay rods with different clay:graphite ratios in aqueous solution and in short reaction time (1 h). The dual role of electrochemical oxidation reaction was presented: (1) the electrochemical oxidation reaction facilitates the exfoliation of pencil graphite leads and in-situ forms functional groups on graphene; (2) the electrochemical oxidation reaction enhances the Faradaic reaction in supercapacitor. The in-situ electrochemical oxidation and functionalization methods can transform low purity graphite to high-value graphene electrode materials for supercapacitors and lithium ion batteries. The specific capacitances of exfoliated graphene are 20-time larger than that of graphite-clay composites. This work provided a value-added way that can transform the low-purity graphite resources to high performance graphene electrode materials. [ABSTRACT FROM AUTHOR]

Both the bonding mode and geometry can serve as the chemical bonding nature of central cation, which is essentially determined by the atomic orbital-hybridization. In this work, we focus on the possible chemical bonding scheme of central cations on the basis of a quantitative analysis of electron domain of an atom. Starting from the hybridization of outer atomic orbitals that are occupied by valence electrons, we studied the possible orbital hybridization scheme of atoms in the periodic table and the corresponding coordination number as well as possible molecular geometries. According to distinct hybrid orbital sets, the chemical bonding of central cations can be classified into three typical types, resulting in the cations with a variety of coordination numbers ranging from 2 to 16. Owing to different hybridization modes, the highest coordination number of cations in IA and IIA groups is larger than that in IB-VIIIB groups, and the coordination number of lanthanide elements is most abundant. We also selected NaNO3, Fe( NO3)3• 9H2O, Zn( NO3)2• 6H2O, Y( NO3)3• 3H2O, and La( NO3)3• 6H2O as examples to confirm the direct relationship between chemical bonding characteristics and orbital hybrid set by IR spectra. The present study opens the door to reveal the chemical bonding nature of atoms on the basis of hybridization and will provide theoretical guides in structural design at an atomic level. [ABSTRACT FROM AUTHOR]

A chemical bonding model is established to describe the chemical potential decrease during crystallization. In the nucleation stage, in situ molecular vibration spectroscopy shows the increased vibration energy of constituent groups, indicating the shortened chemical bonding and the decreased chemical potential towards the formation of nuclei. Starting from the Gibbs free energy formula, the chemical potential decrease during crystallization is scaled, which depends on the released chemical bonding energy per unit phase transition zone. In the crystal growth, the direction-dependent growth rate of inorganic single crystals can be quantitatively determined, their anisotropic thermodynamic morphology can thus be constructed on the basis of relative growth rates. [ABSTRACT FROM AUTHOR]

REPO4 (RE = La, Gd, Lu, Y) serves as an excellent host lattice due to its stable physicochemical properties and optical inertia. Doping Gd3+(La3+) into LuPO4 can form mixed crystals, increasing the Gd3+(La3+) concentration will induce the phase transition from tetragonal to hexagonal lattices, and the variation of the local structure around the Ce3+ activator will influence its 5d-level position and consequently 5d → 4f radiation transition. This can be attributed to the synergy effect of rare earth ions in REPO4, however, the essential mechanism of such a synergy effect on the local structure and optical property is still poorly understood. Here, we study the synergy effect of rare earth ions on the phase transition and PL emission in a Ce3+:REPO4 system on the basis of the relationship between the composition-dependent local structure around Ce3+ and its PL emission properties from a molecular view. The competition between Lu3+ and Gd3+(La3+) in REPO4 not only influences the relative atomic position but also varies the symmetry of anion groups. Infrared absorption bands indicate that the activation of P−O bonding promotes phase transition and enhances PL emission intensity. The PL emission intensity of Ce3+ is higher in a REPO4 host with a lower site symmetry PO43− group (C2) than that with a higher site symmetry PO43− group (D2d). An increased disorder degree in Ce:GdxLu1−xPO4 mixed crystals leads to the shift of the 5d-level of Ce3+ towards a higher position, resulting in the blue shift of the PL emission wavelength. Moreover, the 5d → 4f emission of Ce3+ may also be modulated towards a larger wavelength via substituting the cation site with larger-radius cations under a particular crystallographic structure in REPO4. Our results highlight the importance of disordered local structures as well as activated anion groups in the enhanced PL emission of Ce3+ activators in a host lattice. [ABSTRACT FROM AUTHOR]

Biomass-derived activated carbon electrode materials have been synthesized by carbonization and KOH activation processes from an agriculture waste − rice husk, composed of organic compound and silica. The surface area of activated carbon reached 1098.1 m2/g mainly including mesopores and macropores due to the template effect of silica in rice husk. Owing to the existence of mesopores and macropores, the as-obtained activated carbon materials can be used in aqueous supercapacitors, lithium-ion (Li-ion) capacitors and lithium-sulfur (Li-S) batteries. In KOH electrolyte, fast rate performance (as high as 2 V/s) was obtained due to the existence of ideal electrical double layer capacitance. In organic electrolyte, high voltage (2.5 V) was achieved. Activated carbon electrode for Li-ion capacitor also showed capacity of 17 mAh/g at 100 mA/g with the high voltage range of 2.5 V. The capacities of sulfur-activated carbon in Li-S batteries were 1230 and 970 mAh/g at the current densities of 0.1 and 0.2 C. The present results showed that activated carbon materials with mesopores were good host to immobilize polysulfides. [ABSTRACT FROM AUTHOR]

A general and programmed fast crystallization process (about 12 seconds) was designed to synthesize binary (MOx) and ternary (ABO3, A2BO4) metal oxide nanomaterials with controllable sizes and composition. The fast crystallization process mainly included the burning of metal-nitrate–filter-paper without additional energy supply and it can lead to the formation of exceptionally fine binary and ternary crystallites with sizes of ∼10–20 nm. The thermodynamic reduction potential of the metal-nitrate–filter-paper burning system can be estimated to be between −0.26 and 1.72 V, which can favor the occurrence of redox reactions, i.e. Cu2+→ Cu+→ Cu, Ni2+→ Ni, Co2+→ Co3+, Ce3+→ Ce4+, and Pr3+→ Pr4+. When used as anode materials for lithium-ion batteries, most of the as-burned metal oxides displayed high cycling stability. The discharge capacity of CoO nanoparticles can reach as high as 501.1 mA h g−1 after continuous 50 discharge–charge cycles at a current density of 100 mA g−1. The proposed fast crystallization route provided a versatile, facile and fast method for the synthesis of functional metal oxide nanomaterials with controllable sizes and composition. [ABSTRACT FROM AUTHOR]

Nanoclay assisted electrochemical exfoliation was developed to in-situ form functionalized graphene electrode materials from pencil core with different ratios of graphite and clay. This method made a positive transformation from solid graphite to graphene colloidal solution, which can be used to construct binder- and additive-free thin-film electrodes. Exfoliated graphene can be served as both conductive current collector (film resistance of 33 Ω/square) and electrode materials. Graphene thin-film electrodes from pencil cores displayed higher capacity of 224 than 80 mA h/g of that from pure graphite. The electrochemical performance can be controlled by the ratio of graphite and clay and the oxidation reaction of surface oxygen functional groups. The described nanoclay-assisted electrochemical oxidation route shows great potential for the synthesis of functionalized graphene electrode materials for high-conductive thin-film lithium ion batteries and supercapacitors. [ABSTRACT FROM AUTHOR]

Key issues for supercapacitor electrode materials are their low energy density and slow ion/electron diffusion/transfer kinetics. The formations of nanostructured materials and composite materials with blending/coating conductive additives have been developed to solve above problems. For more efficiently using electroactive metal cations in pseudocapacitance electrode materials, one kind of colloidal supercapacitor electrode materials was introduced to get both high energy and power densities. Colloidal supercapacitor electrode materials have overwhelming advantages, i.e. quasi-ionic state cations, short ion diffusion length and high specific surface area, which is a tradeoff between confined active cations and facile cation diffusion. Multiple-electron transferred Faradaic reactions can occur within the whole colloid, leading to high specific capacitance. The development of colloidal supercapacitor electrode materials can promote the advance of supercapacitors and make their energy densities larger than 100 Wh/kg or more, resulting in replacing batteries. [ABSTRACT FROM AUTHOR]

The effects of crystallization on the formation of geochemical, biological, and synthetic materials have been motivating decades of research into crystal nucleation and growth processes. The development of crystal growth theories and models can deepen the understanding of physicochemical interactions during the crystal growth process, which facilitates the designing of crystallization approaches in material production. The chemical bonding theory of single crystal growth emphasizes the dominant role of dynamic chemical bonding mechanisms at the growing interfaces. In this paper, we highlight the chemical bonding theory of single crystal growth from the chemical reaction viewpoint, by focusing on the atomic level of the growing interface between the liquid and crystal phases. Using ZnO, CeO2, MnO2 and Y3Al5O12 as examples, we review some typical applications of the chemical bonding theory of single crystal growth in calculating crystal habits, evaluating crystal properties, and guiding practical single crystal growth. Microscopically speaking, the essence of crystal growth and design is to create ideal chemical bonding architectures at both the crystal surface and the growing interface via both thermodynamic and kinetic strategies. [ABSTRACT FROM AUTHOR]

We reported a one-step in-situ electrochemical route to synthesize 3D aerogel electrode materials including graphene and hexagonal CeO 2 composites. The graphene/CeO 2 aerogel can be formed via freeze-drying graphene/CeO 2 colloidal solution that was obtained by electrochemical exfoliation of graphite anode and in-situ deposition of CeO 2 nanoparticles on graphene sheets in mixing electrolyte of (NH 4 ) 2 SO 4 /Ce(NO 3 ) 3 and (NH 4 ) 2 SO 4 /(NH 4 ) 2 Ce(NO 3 ) 6 . The as-obtained CeO 2 nanoparticles were closely contacted with graphene, which can enhance the synergistic effect between graphene and CeO 2 . It is interesting that the as-obtained CeO 2 products possessed hexagonal crystal structure that was rarely reported. The Faradaic reactivity of the graphene/CeO 2 composites as supercapacitor was enhanced with the increase of the concentration of Ce salts in initial electrolyte. The introduction of CeO 2 to graphene electrode can lead to the presence of additional pseudocapacitance besides the electric double-layer capacitance. This simple one-step in-situ electrochemical route can be extended to synthesize various graphene/metal oxide aerogel electrode materials for electric energy storage. [ABSTRACT FROM AUTHOR]

Novel colloidal pseudocapacitors are designed using commercially available MnCl 2 salts as starting materials and KOH as electrolyte, where the colloids synthesis and subsequently integrating into practical electrode structures occur at the same spatial and temporal scale. Highly electroactive Mn 7 O 13 ·5H 2 O colloids are formed in-situ by electric field assisted chemical coprecipitation in KOH solution. The highly efficient Faradaic redox reactions involving Mn 3+ ↔ Mn 4+ and Mn 2+ ↔ Mn 3+ are confirmed in electroactive Mn 7 O 13 ·5H 2 O pseudocapacitors, which can deliver high specific capacitance of 2518 F/g based on active Mn cations at current density of 5 A/g. The present results show that instead of one-electron Faradaic reaction, Mn cations in our designed system can lead to two-electron Faradaic reactions. The colloidal pseudocapacitor system involving Mn-based colloids is a novel route to engineer electrochemical performances of inorganic pseudocapacitors. [ABSTRACT FROM AUTHOR]

Both the crystallizing molecule without long-range ordered arrangement and the complex interactions between solvent, anti-solvent, and molecule crystal challenge the imaging of molecule configurations during anti-solvent crystallization. Here, the structural evolution of NH4H2PO4 during anti-solvent crystallization was tracked by in situ ATR-IR spectroscopy. The NH4H2PO4 molecule undergoes D2d→C2v→D2d or C2v→D2d during anti-solvent crystallization, depending on both V(H2O)/V(ethanol) ratio and the concentration of NH4H2PO4 aqueous solution. Moreover, IR spectroscopy can also be used to confirm the anti-solvent role of ethanol in the NH4H2PO4–H2O–ethanol crystallization system. The volatilization of ethanol has been demonstrated as an effective approach to control the dissolution process of NH4H2PO4, which can be used to study the crystallization–dissolution–recrystallization process. The present study can shed light on the anti-solvent crystallization physical and chemistry of NH4H2PO4 from a molecule-level viewpoint. [ABSTRACT FROM AUTHOR]

An excellent CuO/Cu integrated anode with CuO nanoparticle-aggregated microsheets on Cu current collector showed higher capacity beyond the theoretical capacity of CuO. The reoxidation of Cu including converted Cu nanoparticles and Cu current collector into CuO guaranteed the highly reversible conversion reaction and high capacity. The combined current ex-situ methods of XRD, SEM and TEM were used to find the origin of the additional capacity by examining the structural evolution and phase transformation of CuO/Cu integrated anode during electrochemical cycling. After 110 cycles, the discharge capacity of CuO/Cu integrated anode retained a large value of 706 mAh g −1 , which is beyond the theoretical capacity of CuO materials (674 mAh g −1 ). The specific electrode configuration and the release of Cu from integrated Cu current collector made these CuO/Cu electrodes maintain high capacity and cycling stability. The present research demonstrates a protocol for the design of high-performance anode structure: in situ chemical and electrochemical activating integrated electrode system. [ABSTRACT FROM AUTHOR]

We reported the preparation of colloidal graphene in quantity via the anodic exfoliation of graphite in (NH 4 ) 2 SO 4 aqueous solution. In the currently designed electrochemical exfoliation route, mass high-quality graphene was produced within short reaction time, around 1 h. The proposed electrochemical exfoliation mechanism showed that SO 4 2− and H 2 O can be intercalated into those graphite sheets, monolayer and few-layer graphene were obtained by the formation of gaseous SO 2 and O 2 within graphite sheets. Stability evaluation showed that our exfoliated colloidal graphene can be perfectly stabilized in DMF solvent more than 1 week. The colloidal graphene can be used to construct various simple and complex patterns by writing it on A4 paper, which can be applied to flexible printed electronic devices. Furthermore, colloidal graphene can show promising applications in the fabrication of binder- and additive-free electrodes for supercapacitors and lithium-ion batteries. Our present method shows huge potential for industrial-scale synthesis of high-quality graphene and further commercialization of graphene colloid for numerous advanced applications in flexible printed electronics and energy storage devices. [ABSTRACT FROM AUTHOR]

Crystallographically, KDP and ADP have familiar ( H 2 PO 4 - ) n framework, which is formed via hydrogen bonding between H 2 PO 4 - groups along main crystallographic axes. The common characteristics of both KDP and ADP crystallization behaviours are studied from the viewpoint of ( H 2 PO 4 - ) n framework. On the basis of chemical bonding theory of single crystal growth, the anisotropic hydrogen bonding in ( H 2 PO 4 - ) n framework and the chemical bonding between K + / NH 4 + and ( H 2 PO 4 - ) n dominate the anisotropic thermodynamic equilibrium morphology of KDP and ADP. The thermodynamic equilibrium morphology is used to find out the possible preferential growth directions for the dendrite growth of both KDP and ADP, i.e., 〈1 0 0〉 and 〈1 0 1〉 directions. IR spectroscopy of both KDP and ADP solutions with different concentrations has testified our theoretical results, which shows that H 2 PO 4 - ions are initially form ( H 2 PO 4 - ) n framework, and then constituent cations inset into the ( H 2 PO 4 - ) n framework during both KDP and ADP crystallization processes. The present work can provide helpful basic information for the study of crystallization of MH 2 XO 4 crystal family. [ABSTRACT FROM AUTHOR]

Highlights: [•] Novel concept of ionic pseudocapacitor was proposed. [•] Crystallization of YbCl3 in alkaline electrolyte leads to highly electrochemical reactive YbOOH colloids. [•] Crystallization proceeds under chemical coprecipitation and Faradaic redox reactions in YbCl3-KOH supercapacitor system. [•] YbCl3 pseudocapacitors can show ultrahigh capacitance of 2210F/g, and commercial YbCl3 salts can be directly used. [Copyright &y& Elsevier]

The anisotropic growth of large-sizesapphire single crystals alongdifferent pulling directions was studied on the basis of the chemicalbonding theory of single crystal growth and practical Czochralskigrowth. The projection of thermodynamic morphology of sapphire singlecrystal respectively along [210], [110], [001], and [001] rotated57.62° directions can be used to confirm the growth directionsof surfaces that are preferred to be exposed thermodynamically inCzochralski growth. Starting from these thermodynamically preferreddirections, the possible radial directions that are normal to thefour typical pulling directions by kinetic controls have been identifiedby anisotropic chemical bonding distributions of sapphire single crystal.Chemical bonding calculations demonstrate that the lower pulling rateshould be designed when Raxial/Rradial> 1, whereas the higher pulling rateshould be designed when Raxial/Rradial< 1. The anisotropic chemical bondingconditions demonstrate the lowest chemical bonding density along theradial directions of sapphire single crystal when it grows along the[001] pulling direction. Taking [001] as the pulling direction inpractical growth, a ϕ 2″ sapphire single crystal wasgrown via the Czochralski method with a growth rate of 2–3mm/h. Our present work shows the effect of anisotropy on the Czochralskigrowth of large-size single crystals, which can provide a theoreticalguide in practical growth from both thermodynamic and kinetic viewpoints. [ABSTRACT FROM AUTHOR]

Highlights: [•] The ultrahigh specific capacitance of 2060 F/g of Ce(NO3)3 salt was obtained. [•] Water-soluble Ce(NO3)3 salt can be directly used as electrode in KOH electrolyte. [•] In situ chemical and electrochemical activations of Ce(NO3)3-Ni foil function well. [•] Electronegativity can identify the active metal cations with high pseudocapacitance. [Copyright &y& Elsevier]

Highlights: [•] The hydrogen bonding nature during ADP crystallization is studied. [•] The crystallographic structures of and in ADP crystal are discussed. [•] The hydrogen bonding of and is recorded by in situ IR spectrum. [•] Anisotropic chemical bonding conditions dominate ADP crystal morphology. [•] ADP crystal morphologies with different clusters are calculated. [Copyright &y& Elsevier]

We report an electrochemical oxidation route to tunable C/O ratios in the graphene framework, creating enhanced pseudocapacitance with increasing oxygen content. Controlled surface functionalities on graphene enable a high specific capacitance and negligible electric conductivity loss. A specific capacitance of up to 279 F g−1 was achieved for the functionalized graphene at a discharge current of 1 A g−1 in 1 M H2SO4 electrolyte; this capacitance remained as high as 152 F g−1 at 100 A g−1. These values are much higher than those of non-oxidized graphene. These excellent performances of the functionalized graphene signify the importance of precise control of the surface chemistry of graphene-based materials. [ABSTRACT FROM AUTHOR]

Electrochemical capacitors, also known as supercapacitors or ultracapacitors, have received much attention from research and development to industrialization, owing to their promise to deliver high levels of electrical power and offer long operating lifetimes. They are considered ideal candidates for energy storage in high-power applications. Benefiting from intensive nanoscale research in recent decades, remarkable improvements and development of supercapacitive energy storage systems have been achieved. Both the energy density and power density for supercapacitors have been substantially improved. In this review article, we endeavor to assess the profound impacts of nanoscale research on the development of supercapacitors, in terms of the substantial improvement of capacitive performance for electrode materials, and revolutionary advances in electrode and device configurations. In addition, recent progress in basic energy storage mechanisms and prototypes of supercapacitors are also reviewed, including a new kinetically-favored intercalation mechanism introduced for the first time. The review concludes with descriptions of the demonstration of already-realized practical applications of commercially-available supercapacitor devices, especially focusing on real usage in vehicles that are highly anticipated by future communities to further heighten the wide attention on clean energy storage systems. [ABSTRACT FROM PUBLISHER]

Abstract: In this article, we briefly summarized our recent work on the studies of crystallization and functionality of inorganic materials. On the basis of the chemical bonding theory of single crystal growth, we can quantitatively simulate Cu2O crystallization processes in solution system. We also kinetically controlled Cu2O crystallization process in the reduction solution route. Lithium ion battery and supercapacitor performances of some oxides such as Co3O4 and MnO2 were shown to elucidate the important effect of crystallization on functionality of inorganic materials. This work encourages us to create novel functionalities through the study of crystallization of inorganic materials, which warrants more chances in the field of functional materials. [Copyright &y& Elsevier]

Sodium niobate (NaNbO3) microcrystals were crystallized by a technically flexible ion exchange method in solution phase. A potassium niobate hollow sphere (KNHS) precursor was first grown viaa hydrothermal route, the metastable compound is chemically active in NaOH solution, leading to the crystallization of NaNbO3microcrystals by a spontaneous ion exchange and recrystallization process. The crucial influences of ion exchange duration, NaOH concentration, surfactant, and reaction medium (water, ethylene glycol/water, ethylenediamine/water) on both the morphology and crystal phase of the NaNbO3microcrystals have also been established. This current chemical route provides an extremely simple, mild, and effective recipe to crystallize NaNbO3, which could possibly be expanded to more niobate crystals with well controlled chemical compositions, structures, and particle morphologies. [ABSTRACT FROM AUTHOR]

Abstract: Uniform single-crystalline SnS nanobelts have been prepared via a simple wet-chemical route, in which SnCl2 was used as tin source and Na2S as sulfur source. Direct conversion of these SnS nanobelts with two pyramidal tips to porous-walled SnO2 nanocapsules was achieved by oxidizing in atmospheric ambient at 500–700°C. The formation mechanism of these porous nanocapsules is a combination of non-equilibrium interdiffusion, volume loss, and gas release. With these uniform SnS nanobelts as precursors, carbon-coated metal Sn nanorods (Sn@C core-shell structure) were also synthesized by decomposition of sulfide SnS nanobelts with carbon coatings in N2 atmosphere. A strong UV emission peak at 365nm is demonstrated for the SnO2 porous nanocapsules, which makes these promising materials for applications such as optical sensors. Furthermore, energy storage performances of these Sn-based nanomaterials (porous SnO2 nanocapsules and Sn@C core-shell nanocomposites) as anodes for Li-ion batteries were investigated in detail. [Copyright &y& Elsevier]

Novel three-dimensional (3D) branched nanotubes of sodium niobate (NaNbO3) were produced by a multi-step reaction, which involves the synthesis of Nb2O5 branched nanowires and subsequently treating these precursors in alkali solution. XRD and SEM have been used to analyze current products. All the obtained nanobranches exhibited tubular structure, which was induced by nanoscale Kirkendall effect and surface diffusion. This work demonstrates a simple and efficient pathway to design hierarchical and complex hollow nanostructures, which are expected to have important applications, such as sensors and photocatalysts. [ABSTRACT FROM AUTHOR]

ZnO nanosheet and nanorod arrays were selectively synthesized on zinc substrate through the reaction of zinc foil with dilute alkaline solution at 120–180°C for 12–24 h. The microscopic morphology and crystal phase of these products were characterized by scanning electron microscopy (SEM), and X-ray powder diffraction (XRD). The growth mechanism and morphology evolution of the nanostructured ZnO arrays were investigated. Due to their uniform morphologies and large surface areas, the as-prepared ZnO nanosheet and nanorod arrays may be used as photovoltaic films and gas sensors for future applications. [ABSTRACT FROM AUTHOR]

Abstract: Hollow micro-sized H2(H2O)Nb2O6 spheres constructed by nanocrystallites have been successfully synthesized via a bubble-template assisted hydrothermal process. In the reaction process, H2O2 acts as a bubble generator and plays a key role in the formation of the hollow structure. An in situ bubble-template mechanism has been proposed for the possible formation of the hollow structure. The spherelike assemblies of these H2(H2O)Nb2O6 nanoparticles have been transformed into their corresponding pseudohexagonal phase Nb2O5 through a moderate annealing dehydration process without destroying the hierarchical structure. Optical properties of the as-prepared hollow spheres were investigated. It is exciting that the absorption edge of the hollow Nb2O5 microspheres shifts about 18nm to the violet compared with bulk powders in the UV/vis spectra, indicating its superior optical properties. [Copyright &y& Elsevier]

Abstract: A chemical strategy has been purposely designed to hierarchically assemble nanoscale building blocks at the interface of solution/solid. Typically, a solution containing precursor of one component and a metal foil as metal source of another component were employed, on the basis of proposed chemical reactions on expected interfaces. Proper reaction parameters including temperature, pH value etc. were selected to adapt both chemical reactions in solution and on the metal surface. Consequently, at the interface of solution and metal foil, two kinds of nanoscale building blocks deposited simultaneously leading to the current hierarchical assembly. This strategy has been applied to the fabrication of a series of functional materials, including Nb2O5/TiO2, Nb2O5/LiF and ZnO/Co3O4. The current strategy provides a convenient one-step route to achieve complex functional structures, which may have potential applications in a variety of fields such as solar cells, Li-ion batteries, electrochemical supercapacitors, catalysts as well as chemical, gas, and bio-sensors. [Copyright &y& Elsevier]

Abstract: Covellite copper sulfide (CuS) micro/nanometer crystals in the shape of hierarchical doughnut-shaped, superstructured spheric-shaped and flowerlike architectures congregated from those nanoplates with the thickness of 20–100nm have been prepared by a solvothermal method. The as-obtained CuS products were characterized by means of scanning electron microscopy (SEM), X-ray diffractometry (XRD) and energy-dispersive X-ray spectroscopy (EDS). A systematic investigation has been carried out to understand the factors influencing the evolution of CuS particle morphology which found to be predominant by solvent, surfactant, sulfur resource and copper salt. The possible formation mechanism for the nanostructure formation was also discussed. These CuS products show potential applications in solar cell, photothermal conversion and chemical sensor. [Copyright &y& Elsevier]

Abstract: Morphology-tuned ZnO microcrystals can be prepared by oxidizing zinc metal substrates in aqueous solution using hydrothermal technique. Some typical ZnO growth morphologies such as nanorod superstructures, nanorod arrays, microspheres, hierarchical nanostructures, and split crystals have been chemically fabricated. These microscopic shapes can be finely controlled by selecting Zn(NO3)2 concentration and solvent. A conceptual model was proposed to explain the formation of the as-prepared ZnO structures by selecting proper kinetic environments. This one-step, wet-chemical approach is controllable and reproducible, which can be conveniently transferred to industrial applications. [Copyright &y& Elsevier]

Abstract: An alcohol thermal technique was applied to the controlled growth of hexagonal ZnO architectures via selective chemical etching. ZnO microdisks were produced first under mild alcohol thermal conditions in presence of formamide. Due to a higher surface energy/atomic density of Zn2+ {0001} than that of the other faces, hexagonal ZnO microring was obtained by selectively etching positive polar surface of disk-like precursor with a high density of planar defects at the center. The selective etching of ZnO is related to its crystallographic characteristics of surface polarity and chemical activities, which opens a new opportunity for the shape-controlled synthesis of wurtzite-structured materials. [Copyright &y& Elsevier]

Well-defined CdS branched nanorod arrays on ITO glass were fabricated via a facile one-step hydrothermal approach in large scale employing cadmium sulfide and thiourea as starting agents. Structural and morphological evolutions of CdS branched nanorod arrays were studied by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. A formation mechanism of the hierarchical structure via this one-step synthesis was tentatively studied by investigating the reaction time. Tree-like nanostructures can also be obtained at relative higher reaction temperatures. As CdS can directly grow on transparent conductive substrate, the product obtained here should have potential applications in optoelectric devices such as solar cells and light sources. [ABSTRACT FROM AUTHOR]

Nanostructured materials with controlled architectures are desirable for many applications, among which, metal oxides are especially important in optics, electronics, biology, catalysis, and energy conversions. Various chemical routes have been widely investigated for the synthesis of nanostructured metal oxide particles and films. More recently, deliberately designed chemical strategies have been used to produce particles and films composed of more complex crystal structures. In this paper, we discuss some recent progresses in the design of complex nanostructures through chemical routes, emphasize particularly on metal oxides. We first review some basic concepts involved in the fabrication of complex nanostructures, including crystal nucleation and growth, shape controlling and ripening process. We then describe more recent work on the use of different methods to synthesize a wide range of complex nanostructures, including hierarchical structures, heterostructures, as well as oriented nanowires and nanotubes. Such purposely built materials are designed, and engineered to match the physical, chemical, and structural requirements of their applications. [ABSTRACT FROM AUTHOR]

Abstract: Large-scale, well-aligned, and oriented semiconductor ZnSe nanobelt arrays have been achieved via the thermal treatment of belt-like precursor (ZnSe·ethylenediamine), which has been synthesized by a simple template-free solvothermal route. ZnSe nanobelts grow perpendicularly on zinc substrate, with thickness of about 50 nm, widths of several hundreds of nanometers, and lengths of up to several micrometers. The as-obtained products have been characterized by scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray, and photoluminescence spectrometer. The cooperative action of the mixed solvents is responsible for the formation of the morphology of the resulting ZnSe nanobelt arrays. Room-temperature photoluminescence measurement indicates that the as-obtained ZnSe nanobelt arrays have a strong emission peak centered at 578 nm and two weak emission peaks centered at 420 and 433 nm. The strong emission from the unique well-aligned ZnSe nanostructures reveals their potential as building blocks for optoelectronics devices. [Copyright &y& Elsevier]

Abstract: Three methods were employed to produce specific Mg(OH)2 (MH) granules with improved filtration efficiency, using crystallization technique. A buffer solution was utilized to improve the crystallization of MH, the spherical assembly composed of both nanosheets and hollow microspheres was obtained. A hydrothermal treatment of amorphous MH led to MH hexagonal nanoplates. In a directing growth, SO4 2− ions were found to strongly improve the crystallization of MH. In the current work, one-dimensional 5Mg(OH)2·MgSO4 ·2H2O whiskers and MH microspheres can be crystallized on a large scale. The filtration tests show that these specific MH granules have improved filtration properties. The current work opens up a new avenue for the production of MH granules, and the optimal filtration efficiency offers a significant control over the quality of MH-type products. [Copyright &y& Elsevier]

Abstract: Semiconductor CuS hollow spheres by self-assembly coupled with bubble templating through a facile one-step solvothermal route has been demonstrated. An energy-minimizing-driven self-assembly of CuS nanoparticles on the base of H2S bubbles is responsible for the formation of the hollow structure. The as-obtained CuS products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and UV–vis–NIR spectrophotometer. Due to the unique optical property, these hollow structures are envisaged to be used in applications such as novel building blocks for the advanced materials, catalysis, solar cell devices, and drug delivery system. [Copyright &y& Elsevier]

The concept of electronegativity (EN), which was proposed by Pauling in 1932, is closely related to such properties of molecules as the polarizability, hardness (softness) and charge distribution, and is an important theoretical basis for judging the properties of substances. With the development of new materials and the increase of interdisciplinary cooperation, EN has been a basic atomic parameter which is widely used in the fields of chemistry, physics and materials science. The development of EN has involved three stages, atomic EN, ionic EN and bond EN. The ionic EN, which is the EN values of elements in different valence states by including the chemical environment of atoms, accurately describes various physical and chemical properties of ions and compounds. The bond EN is a bridge linking atomic EN and the properties of materials, which helps us to establish the quantitative correlation between macroscopic properties and microscopic electronic structures of materials. The concepts of ionic EN and bond EN broaden the scope of EN theory, and play important roles in the design of novel materials. This paper presents a detailed introduction of a new development of EN and its applications in materials research. [ABSTRACT FROM AUTHOR]

Based on the electron-holding energy per unit volume, we extend the concept of hardness to atomic stiffness, ionic stiffness and bond hardness, investigating the nature of material hardness at these three levels. We find that the stiffness of isolated atoms or ions has no direct connection with the hardness of materials, whereas material hardness is directly related to bond hardness, which is essentially determined by the electron-holding energy of its constituent chemical bonds per unit volume. We establish a model for identifying the hardness of materials on the basis of bond hardness. This work offers a deeper understanding of the nature of material hardness at the atomic level, and provides a practical guide in the search for new superhard materials. [ABSTRACT FROM AUTHOR]

Abstract: Crystal engineering allows us to predict and control the packing of molecular building units in solid state, which has been attracting much attention due to its exploitation for the synthesis of crystalline materials with novel structures and promising properties. The crystal engineering strategies toward the synthesis of high-nuclearity lanthanide clusters and three-dimensional (3D) lanthanide–transition-metal (Ln–M) coordination polymers were well discussed in the present work. It has shown that the high-nuclearity lanthanide clusters can be rationally synthesized by surface modification strategy. On the basis of the different coordination nature of lanthanide and transition-metal ions, the multifunctional organic ligands with mixed coordination sites such as isonicotinate have been elaborately selected to rationally construct a series of homochrial and achiral 3D Ln–M coordination frameworks built from inorganic heterometallic chains with improved thermal stability. Furthermore, novel 3D Ln–M coordination frameworks have been built from discrete lanthanide clusters (or cluster polymers) and transition-metal clusters (or cluster polymers) by faultlessly harmonizing the subtle relationship between these two different types of metal cluster or cluster polymer units. The current work offers us great potential toward the pursuit of rational synthesis of Ln–M coordination assemblies on the basis of crystal engineering principles. [Copyright &y& Elsevier]

Abstract: A novel rapid crystal growth system was conveniently constructed on the basis of the high-speed acquisition card and the Laboratory Virtual Instrument Engineering Workbench software. All growth parameters were real-time monitored and controlled to provide a stable environment with small fluctuation for crystal growth. A simple equation was derived from the solution properties to calculate the cooling curves corresponding to different growth parameters. The combination of the calculated cooling curve and our designed growth system can lead to the rapid growth of potassium dihydrogen phosphate crystal routinely. [Copyright &y& Elsevier]

Abstract: A new strategy has been successfully designed for the first time to synthesize ZnO nanorod arrays on a zinc surface by employing a novel NaCl solution corrosion-based approach. The natural oxidation of zinc metal by naturally dissolved oxygen in water is very slow due to the surface oxide layer. However, in the presence of NaCl solution, this spontaneous oxidation reaction can be accelerated drastically, and thus ZnO nanorod arrays can readily grow along the [001] direction on the surface of the zinc foil. In particular, this simple synthetic strategy only requires NaCl solution and zinc foil, which enables us to generate, at large scale, low cost, and moderate temperature, advanced thin films. Photoluminescence (PL) spectrum reveals that our obtained ZnO nanorods have negligible oxygen vacancies. By the way, a two-dimensional pattern of flower-like ZnO nanosheets on Zn by formamide-induced sequential nucleation and growth on zinc foil substrate has also been demonstrated. [Copyright &y& Elsevier]

Abstract: The mixed crystals of ammonium dihydrogen phosphate (ADP) and potassium dihydrogen phosphate (KDP) with different growth morphologies have been prepared and investigated by X-ray diffraction experiments. All the obtained samples crystallize in the tetragonal system with a continuous expansion of unit cell when increasing ammonium content. The different characteristics of potassium and ammonium lead to the deformation of crystal structure, production of internal stress and degradation of the obtained crystal quality. When ammonium or potassium content in the mixed crystal is low, the accumulated internal stress is weaker and the mixed crystals with high quality can be grown. Contrarily, in the intermediate composition, especially around 65 percent ammonium, the strongest internal stress results in the intensive distortion of crystal lattice and consequent cracks within the mixed crystals. The microscopic mechanism of the morphology evolution of the mixed crystals is proposed and calculated in the chemical bond viewpoint and bond valence model, the difference of the average valence electron density between the KDP and ADP dominates their different growth morphologies. [Copyright &y& Elsevier]

Abstract: A low-temperature and effective precursor-based method has been demonstrated to synthesize nanostructured ZnO and its precursors with controllable morphology. It is found that the morphology of ZnO precursors has a strong dependence on the reaction conditions that include the molar ratio of reagents, solvent, and reaction temperature. Ethylene glycol used as an organic capping reagent is the key to determine the two-dimensional petal-like ZnO nanostructure. The structures and properties of the obtained-samples are characterized by a scanning electron microscope, an X-ray diffractometer, and an energy dispersive X-ray spectrometer. The present technique is an easy and cheap method to synthesize nanoscale photonic and electronic materials. [Copyright &y& Elsevier]

Abstract: The ideal growth morphologies of NH4H2PO4 and MgO crystals are calculated on the basis of the structural analysis and the bond valence model. By considering the surface structure, the bonding process within the boundary layer and the evolution of growth units, the actual crystal morphologies can be conveniently modified, which are well in accordance with the obtained crystals. Furthermore, the cleavage property of MgO single crystals is investigated by conducting an X-ray diffraction experiment and the experimental result is also in line with the theoretical calculation. [Copyright &y& Elsevier]