Enhancement of Fluorescence Emission for Tricolor Quantum Dots Assembled in Polysiloxane toward Solar Spectrum-Simulated White Light-Emitting Devices.

Commercial white light-emitting diodes (LEDs) have the undesirable characteristics of blue-rich emission and low color rendering index (CRI), while the constituent quantum dots (QDs) suffer from aggregation-induced fluorescence quenching and poor stability. Herein, a strategy is developed to assemble tricolor QDs into a polysiloxane matrix using a polymer-mediated hybrid approach whereby the hybrid composite exhibits a significant enhancement of aggregation-dispersed emission, outstanding photostability, high thermal stability, and outstanding fluorescence recovery. Using the as-prepared hybrid fluorescent materials, the fabricated LEDs exhibit solar spectrum-simulated emission with adjustable Commission Internationale de L'Eclairage coordinates, correlated color temperature, and a recorded CRI of 97. Furthermore, they present no ultraviolet emission and weak blue emission, thus indicating an ideal healthy and high-CRI white LED lighting source.

Sol-gel-Derived highly sensitive optical oxygen sensing materials using Ru(II) complex via covalent grafting strategy.

The preparation and oxygen sensing properties of Ru(ll) covalently-grafted and physically-incorporated silica based hybrid materials by sol-gel technique are described in this article. The Ru(II) complexes are successfully grafted onto the backbone of the silica via the condensation reaction of the tetraethoxysilane and the functionalized Ru(II) complex 2-[4'-{3-(Triethoxysilyl)propyl}phenyl]imidazo [4,5-f]-1,10-phenanthroline that contains the hydrolysable tri-alkoxylsilyl group. The luminescence quenching of Ru(II) complex by oxygen within the silica matrix is efficient. The oxygen quenching sensitivity of the covalently-grafted sample is higher than that of the physically-incorporated one due to the strong Si-CH2 bond that is useful to prolong the excited state lifetimes and enhance the photobleaching of the luminophore. The downward oxygen sensing Stern-Volmer plots can be well fitted using the Demas two-site model and the Lehrer model due to the heterogeneous distribution of the Ru(ll) complex within the sol-gel derived silica.

A mild method to prepare nitrogen-rich interlaced porous carbon nanosheets for high-performance supercapacitors.

In this work, a non-toxic and mild strategy was presented to efficiently fabricate porous and nitrogen-doped carbon nanosheets. Silkworm cocoon (SCs) acted as carbon source and original nitrogen source. Sodium carbonate (Na2CO3) could facilitate the SCs to expose silk protein and played a catalytic role in the subsequent activation of calcium chloride (CaCl2). Calcium chloride served as pore-making agent. The as-obtained carbon materials with protuberant porous nanosheets exhibit high specific surface area of 731 m2 g-1, rich native nitrogen-doped of 7.91 atomic %, wide pore size distribution from 0.5 to 65 nm, and thus possessing high areal specific capacitances of 34 µF cm-2 as well as excellent retention rate of 97% after 20 000 cycles at a current density of 20 A g-1 in 6 M KOH electrolyte. The assembled carbon nanosheet-based supercapacitor displays a maximum energy density of 21.06 Wh kg-1 at the power density of 225 W kg-1 in 1 M Na2SO4 electrolyte. Experimental results show that a mild and non-toxic treatment of biomass can be an effective and extensible method for preparing optimal porous carbon for electrochemical energy storage.

Calcium-chloride-assisted approach towards green and sustainable synthesis of hierarchical porous carbon microspheres for high-performance supercapacitive energy storage.

Spherical carbon materials exhibit great competence as electrode materials for electrochemical energy storage, owing to the high packing density, low surface to volume ratio, and excellent structure stability. How to utilize renewable biomass precursor by green and efficient strategy to fabricate porous carbon microspheres remains a great challenge. Herein, we report a KOH-free and sustainable strategy to fabricate porous carbon microspheres derived from cassava starch with high specific surface area, high yield, and hierarchical structure, in which potassium oxalate monohydrate (K2C2O4·H2O) and calcium chloride (CaCl2) are employed as novel activator. The green CaCl2 activator is crucial to regulate the graphitization degree, specific surface area, and porosity of the carbon microspheres for improving the electrochemical performance. The as-prepared carbon microspheres exhibit high specific surface area (1668 m2 g-1), wide pore size distribution (0.5-60 nm), high carbon content (95%), and exfoliated surface layer. The hierarchical porous carbon microspheres show high specific and areal capacitance (17.1 µF cm-2), superior rate performance, and impressive cycling stability. Moreover, the carbon microspheres based symmetric supercapacitor exhibits high capacitance and excellent cycling performance (100% after 20 000 cycles at a current density of 5 A g-1). This green and novel approach holds great promise to realize low-cost, high-efficient and scalable of renewable cassava starch-derived carbon materials for advanced supercapacitive energy storage applications.

The changing structure by component: Biomass-based porous carbon for high-performance supercapacitors.

In this work, a simple and efficient method is introduced to prepare biomass-based porous carbon with excellent performance by changing the content of component (e.g., cellulose, hemicellulose, lignin, and extractives) of the raw materials. When the content of the components change, the corresponding carbon skeleton will be separated, resulting in a structure that is conducive to activation conditions. Using bagasse with fiber tubular structure as carbon precursor, the synthetic hierarchical porous carbon (BHPC-4) possesses a high specific surface area (SSA) of 3135 m2 g-1 more than the control sample (2484 m2 g-1). Benefitting from the improvement of the structure, the BHPC-4 electrode exhibits an appealing capacitance of 410.5F g-1 at 0.5 A g-1 and long-term cycling stability of 100% capacitance retention after 10,000 cycles in the 6.0 M KOH system. Furthermore, a delightful energy density of 25.6 Wh kg-1 at a 226 W kg-1 can be achieved in 1.8 V Na2SO4 aqueous symmetrical supercapacitors. This method has universal significance in preparing high-porosity and high-performance biomass-based carbon materials for various energy storage/conversion.

Engineering of nanonetwork-structured carbon to enable high-performance potassium-ion storage.

Potassium-ion batteries (KIBs) have been developed as an emerging electrochemical energy storage device due to the low cost and abundant resource of potassium. However, they suffer insufficient cyclability and poor rate capability caused by the large K+, severely limits their further applications. Herein, a nanonetwork-structured carbon (NNSC) is reported to address the issue. Cycling stability with very low decay rate of 0.004% per cycle over 2000 cycles and excellent rate capability (i.e., 261 mAh g-1 at 100 mA g-1 and 108 mAh g-1 at 5000 mA g-1) are achieved. The superior performance is attributed to the unique structure of NNSC, in which the three-dimensional interconnected hierarchical porous structure with hollow nanosphere as network units not only can effectively alleviate the volume expansion induced by the insertion of large K+, but also can offer fast pathways for K+ diffusion. In addition, the local graphitized carbon shell of NNSC can promote conductivity of material and reduce the resistance to K+ transportation. Thus, the NNSC has great potential in developing stable-structure and high-rate electrodes for next generation KIBs.

Improved ion-diffusion performance by engineering an ordered mesoporous shell in hollow carbon nanospheres.

A new kind of hollow carbon nanosphere with an ordered mesoporous shell structure is prepared and demonstrated to have improved performances in practical application areas involving fast ion transport.

Small nitrogen-doped carbon dots as efficient nanoenhancer for boosting the electrochemical performance of three-dimensional graphene.

As a new class of zero-dimensional carbon nanomaterials, carbon dots have triggered intensive research interest in various fields. However, the low surface area, hydrophilicity, and agglomeration characteristics limit their applications in energy storage fields. Herein, we demonstrate that nitrogen-doped carbon dots can be employed as efficient nanoenhancer to boost the electrochemical performance of three-dimensional graphene. The as-prepared materials exhibit an interconnected framework with abundant oxygen- and nitrogen-containing functional groups, which enable fast penetration and transport of electrolyte ions and provide more active sites and electric conductivity. Employed as binder-free electrode for supercapacitors, the resultant materials present high specific capacitance (338 F g-1) and areal capacitance (604 µF cm-2) at a current density of 0.5 A g-1, which is much higher than that of pristine three-dimensional graphene (190 F g-1, and 114 µF cm-2), with an enhancement of 78% and 430%, respectively. Moreover, superior long-term cycling stability (94% of capacitance retention after 20 000 charging/discharging cycles at 10 A g-1) as well as improved electric conductivity can also be achieved. These results certify that nitrogen-doped carbon dots can be applied as nanobooster to comprehensively improve the performance of graphene for high-performance electrochemical energy storage.

Facile construction of hollow carbon nanosphere-interconnected network for advanced sodium-ion battery anode.

Sodium-ion batteries are promising next-generation electrical-energy-storage devices due to the relative low cost, and the natural abundance of sodium resources. Yet developmental anodes in sodium-ion batteries such as carbonaceous materials have adagio sodium ion diffusion kinetics, huge volume expansion, poor rate performance and cycle stability. Herein, we report a high-performance sodium ion storage anode material, i.e., a unique nanonetwork-structured carbon (NNSC) with a valuable hollow nanosphere as network unit by developing a facile, efficient and post-treatment-free strategy. The as-constructed NNSC exhibits a three-dimensional interconnected hierarchical porous network and a luxuriant accessible surface area, which greatly enhance sodium ion transport and storage. Thus, the obtained NNSC demonstrates excellent sodium ion storage performance, including a high capacity of 250 mA h g-1, good rate capability, and ultra-long-term cycle life up to 9000 cycles. Such attractive capabilities could accelerate the application of sodium-ion batteries in large-scale energy storage.

Extraordinary Thickness-Independent Electrochemical Energy Storage Enabled by Cross-Linked Microporous Carbon Nanosheets.

Two-dimensional carbon-based nanomaterials have demonstrated great promise as electrode materials for electrochemical energy storage. However, there is a trade-off relationship between energy storage and rate capability for carbon-based energy storage devices because of the incrementing ion diffusion limitations, especially for thick electrodes with high mass loading. Herein, we report the cross-linked microporous carbon nanosheets enabling high-energy and high-rate supercapacitors. The as-fabricated microporous carbon nanosheets exhibit an extraordinary thickness-independent electrochemical performance. With the thickness of 15 µm, the as-fabricated carbon nanosheet electrode possesses areal/volumetric/gravimetric capacitance of 895 mF cm-2/596 F cm-3/358 F g-1. Even at a high electrode thickness of 125 µm, the as-fabricated thick electrode presents an ultrahigh areal/volumetric/gravimetric capacitance of 4102 mF cm-2/328 F cm-3/328 F g-1. Furthermore, the as-assembled symmetric supercapacitor delivers an outstanding energy density of 19.2 W h kg-1 at a power density of 135 W kg-1 and ultralong cycling stability (capacitance retention of 95% after 180 000 charge/discharge cycles) in an alkaline electrolyte. This work not only provides a facile method for low-cost preparation of carbon nanostructures and high-value utilization of biomass wastes but also offers new insights into rational design and fabrication of advanced electrode materials for high-performance electrochemical energy storage.

Advanced nanonetwork-structured carbon materials for high-performance formaldehyde capture.

Facile design and construction of advanced materials for eliminating the indoor formaldehyde pollution is still a great challenge but very desirable to provide clean air for human life. Herein, we report a high-performance formaldehyde adsorbent, i.e., a new type of nanonetwork-structured carbon (NNSC) with a hollow nanosphere as network unit by developing a facile, efficient and post-treatment-free strategy. The NNSCs can be easily obtained by a simple carbonization of a mixture, in which natural wheat husk and Teflon are used as carbon precursor and biotemplate-in-situ-remover, respectively. The as-constructed NNSC exhibits a unique three-dimensional interconnected micro-, meso- and macroporous nanonetwork. Benefiting from such a valuable hollow nanosphere-interconnected network structure, the NNSCs show surprising formaldehyde gas adsorption properties including super-high storage capacity, ultrafast adsorption rate and efficient adsorptively active surface. Remarkably, their specific adsorption capacity and maximum adsorption rate are as high as 120.3 mg g-1 m-3 and 44.6 mg g-1 m-3 h-1, which make 18-fold and 41-fold enhancement when compared to activated carbon commercially used for formaldehyde adsorption, respectively. This work highlights an efficient solution to develop high-performance formaldehyde adsorbents by facile and rational construction of novel porous structure, simultaneously to provide a new avenue to high-value advanced materials for challenging environmental issue.

Interconnected 3 D Network of Graphene-Oxide Nanosheets Decorated with Carbon Dots for High-Performance Supercapacitors.

Interconnected 3 D nanosheet networks of reduced graphene oxide decorated with carbon dots (rGO/CDs) are successfully fabricated through a simple one-pot hydrothermal process. The as-prepared rGO/CDs present appropriate 3 D interconnectivity and abundant stable oxygen-containing functional groups, to which we can attribute the excellent electrochemical performance such as high specific capacitance, good rate capability, and great cycling stability. Employed as binder-free electrodes for supercapacitors, the resulting rGO/CDs exhibit excellent long-term cycling stability (ca. 92 % capacitance retention after 20 000 charge/discharge cycles at current density of 10 A g-1 ) as well as a maximum specific capacitance of about 308 F g-1 at current density of 0.5 A g-1 , which is much higher than that of rGO (200 F g-1 ) and CDs (2.2 F g-1 ). This work provides a promising strategy to fabricate graphene-based nanomaterials with greatly boosted electrochemical performances by decoration of with CDs.

Temperature and Oxygen Sensing Properties of Ru(II) Covalently-Grafted Sol-Gel Derived Ormosil Hybrid Materials.

In this article, oxygen and temperature-sensing hybrid materials consisting of [Ru(Phen)3]2+ portions covalently-grafted onto the sol-gel derived ormosil network were prepared by co-condensation of tetraethoxysilane (TEOS) using n-octyltriethoxysilane as the network modifier. For comparison purposes, the hybrid materials in which [Ru(Phen)3]2+ were conventionally physically-incorporated into the matrix were also prepared. The obtained hybrid materials were characterized by Fourier transform infrared (FT-IR), luminescence intensity oxygen quenching Stern-Volmer plots, temperature quenching plots and excited-state lifetime. The near linear Stern-Volmer plots can be attributed to the approximate heterogeneous environment of the luminophore within the ormosil materials. The results reveal that the. covalently-grafted sample is more sensitive to 02, and has a higher sensing sensitivity and a higher thermal activation energy compared to the physically-incorporated one, since these Ru(II) molecules are strongly covalently-grafted onto the Si-O network via the CH2-Si bonds and less -OH group.

Facile Synthesis of Three-Dimensional Heteroatom-Doped and Hierarchical Egg-Box-Like Carbons Derived from Moringa oleifera Branches for High-Performance Supercapacitors.

In this paper, we demonstrate that Moringa oleifera branches, a renewable biomass waste with abundant protein content, can be employed as novel precursor to synthesize three-dimensional heteroatom-doped and hierarchical egg-box-like carbons (HEBLCs) by a facile room-temperature pretreatment and direct pyrolysis process. The as-prepared HEBLCs possess unique egg-box-like frameworks, high surface area, and interconnected porosity as well as the doping of heteroatoms (oxygen and nitrogen), endowing its excellent electrochemical performances (superior capacity, high rate capability, and outstanding cycling stability). Therefore, the resultant HEBLC manifests a maximum specific capacitance of 355 F g-1 at current density of 0.5 A g-1 and remarkable rate performance. Moreover, 95% of capacitance retention of HEBLCs can be also achieved after 20 000 charge-discharge cycles at an extremely high current density (20 A g-1), indicating a prominent cycling stability. Furthermore, the as-assembled HEBLC//HEBLC symmetric supercapacitor displays a superior energy density of 20 Wh kg-1 in aqueous electrolyte and remarkable capacitance retention (95.6%) after 10 000 charge-discharge cycles. This work provides an environmentally friendly and reliable method to produce higher-valued carbon nanomaterials from renewable biomass wastes for energy storage applications.

A Self-Quenching-Resistant Carbon-Dot Powder with Tunable Solid-State Fluorescence and Construction of Dual-Fluorescence Morphologies for White Light-Emission.

Self-quenching in the aggregation state is overcome, and tunable solid-state photoluminescence of carbon-dot powder is achieved. Furthermore, based on the controllable optical property in organic solvents, a novel concept, i.e., constructing dual-fluorescence morphologies from single luminescent species, is presented to realize white-light emission.

Amorphous Ni-Co Binary Oxide with Hierarchical Porous Structure for Electrochemical Capacitors.

A simple and outstanding approach is provided to fabricate amorphous structure Ni-Co binary oxide as supercapacitors electrode materials. We can easily obtain porous Ni-Co oxides composite materials via chemical bath deposition and subsequent calcination without any template or complicate operation procedures. The amorphous porous Ni-Co binary oxide exhibits brilliant electrochemical performance: first, the peculiar porous structure can effectively transport electrolytes and shorten the ion diffusion path; second, binary composition and amorphous character introduce more surface defects for redox reactions. It shows a high specific capacitance up to 1607 F g(-1) and can be cycled for 2000 cycles with 91% capacitance retention. In addition, the asymmetric supercapacitor delivers superior energy density of 28 W h kg(-1), and the maximum power density of 3064 W kg(-1) with a high energy density of 10 W h kg(-1).

Simple, green and high-yield production of single- or few-layer graphene by hydrothermal exfoliation of graphite.

Graphene is widely used as promising electronic material and devices, owing to its exceptional electronic and optoelectronic properties. Up to now, defect-free graphene has been limited to the method for controllable, reproducible and scalable mass production. A simple, green, and nontoxic approach for large-scale preparation of high quality graphene is produced by exfoliation of graphite sheets collaborated with intercalant (FeCl2) under hydrothermal conditions, the absence of defects or oxides in graphene with a yield up to 10 wt% can be a practical application and industrial process such as optical limiters, transparent conductors, and sensors. This new process could potentially be improved to give a yield of up to 35 wt% of the starting graphite mass with sediment recycling. We show with experiments and theories that exfoliation graphene is the result of a combined action by diminishing the van der Waals interactions between graphite layers and the shear force drove by the Brownian motion of H2O and FeCl2 molecules. Hydrothermal exfoliation has potential applications in the exfoliation of other layered materials (e.g. BN, MoS2) and carbon nantubes, and in the synthesis of intercalation compounds, nanoribbons, and nanoparticles, thus opening new ways of exfoliation engineering.

Simple additive-free method to manganese monoxide mesocrystals and their template application for the synthesis of carbon and graphitic hollow octahedrons.

Mesocrystals are of great importance owing to their novel hierarchical microstructures and potential applications. In the present work, a simple additive-free method has been developed for the controllable synthesis of manganese monoxide (MnO) mesocrystals, in which cheap manganese acetate (Mn(Ac)2) and ethanol were used as raw materials without involving any other expensive additives such as surfactants, polyelectrolyte, or polymers. The particle size of the resulting MnO mesocrystals is tunable in the range 400-1500 nm by simply altering the concentration of Mn(Ac)2 in ethanol. The percentage yield of the octahedral MnO mesocrystals is about 38 wt % with respect to the starting Mn(Ac)2. The selective adsorption of oligomers, which was resulted from the polymerization of ethanol, acted as an important role for the mesocrystal formation. A mechanism involving the oriented aggregation of MnO nanoparticle subunits and the subsequent ripening process was proposed. Moreover, for the first time, the as-synthesized MnO mesocrystals were employed as a novel template to fabricate functional materials with an octahedral morphology including MnO@C core/shells, carbon, and graphitic hollow octahedrons. This method shows the importance of mesocrystals not only for the field of material research but also for the application in functional materials synthesis.

Microtube bundle carbon derived from Paulownia sawdust for hybrid supercapacitor electrodes.

The structure and capacitive properties of microtube bundle carbons (MTBCs) from carbonization of paulownia sawdust (PS) followed by NaOH activation were investigated. Morphology analyses indicated that MTBCs had abundant micropores and mesopores with a high specific surface area of about 1900 m(2) g(-1). Cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy studies demonstrated the excellent charge storage, transfer capability, and low impedance of MTBCs. The specific capacitance of MTBCs-4 was as high as 227 F g(-1) at 2 mV s(-1). Experimental results indicated that MTBCs provide smooth charge-transfer pathways for the ions in electrolytes and gateways to micropores and mesopores in the bulk. The hybrid supercapacitor model of MTBCs based on electrical double-layer capacitors and electrostatic capacitors was discussed and demonstrated. MTBCs are electrostatic capacitors at low frequency current, and may provide the pathways for easy accessibility of efficient charge transmission and high energy storage.

A simple additive-free approach for the synthesis of uniform manganese monoxide nanorods with large specific surface area.

A simple additive-free approach is developed to synthesize uniform manganese monoxide (MnO) one-dimensional nanorods, in which only manganese acetate and ethanol were used as reactants. The as-synthesized MnO nanorods were characterized in detail by X-ray diffraction, scanning and transmission electron microscopy (TEM) including high-resolution TEM and selected-area electron diffraction, Fourier transform infrared spectrum, and nitrogen adsorption isotherm measurements. The results indicate that the as-synthesized MnO nanorods present a mesoporous characteristic with large specific surface area (153 m2 g-1), indicating promising applications in catalysis, energy storage, and biomedical image. On the basis of experimental results, the formation mechanism of MnO one-dimensional nanorods in the absence of polymer additives was also discussed.