In-Situ Synergistic 2D/2D MXene/BCN Heterostructure for Superlative Energy Density Supercapacitor with Super-Long Life.

The 2D/2D layered materials are gaining much-needed attention owing to the unprecedented results in supercapacitors by their robust structural and electrochemical compatibility. Here, a facile scalable synthesis of 2D/2D MXene/boron carbon nitride (BCN) heterostructure through no residue direct pyrolysis is reported. The process allows the in-situ growth of BCN nanosheets unravelling the surfaces of MXene synergistically that provide an interconnected conductive network with wide potential window, augmented proportion of Ti sites at elevated temperature removing terminal groups enabling high pseudocapacitive activity and impressive stability. As a result, the as-assembled MXene/BCN electrode records a high specific capacitance of 1173 F g-1 (1876 C g-1 ) at 2 A g-1 and an energy density of 45 Wh kg-1 . Further, the fabricated solid-state device exhibits an ultra-high cyclability of 100% capacitive retention after 100 000 cycles. This will be an epitome for future 2D/2D heterostructures with commendable electrochemical properties as an expedient solution for energy storage applications.

Gram-scale synthesis of ZnS/NiO core-shell hierarchical nanostructures and their enhanced H2 production in crude glycerol and sulphide wastewater.

Design and development of the efficient and durable photocatalyst that generates H2 fuel utilizing industrial wastewater under solar light irradiation is a sustainable process. Innumerable photocatalysts have been reported for efficient H2 production, but their large-scale production with the same efficiency of H2 production is a challenging task. In this study, a few gram-scale syntheses of ZnS wrapped with NiO hierarchical core-shell nanostructure via the surfactant-mediated process has been reported. Morphology and crystal structure analysis of ZnS/NiO showed spherical shaped hierarchical core-shell with cubic and face-centered cubic crystal structures. The surface examination confirmed the presence of Zn2+, S2-, Ni2+ and O2- ions in the nanocomposite. The photocurrent and photoluminescence studies of pristine and nanocomposites revealed that core-shell material is non-corrosive with a prolonged life-time of photo-excitons. Parametric studies on photocatalytic H2 generation in lab-scale photoreactor using crude glycerol in water recorded a high rate of H2 generation of 9.3 mmol h-1.g-1 of catalyst under the simulated solar light irradiation. Optimized reaction parameters are extended to a demonstrative photoreactor containing aqueous crude glycerol produced 18.5 mmol h-1 of H2 generation under the natural solar light irradiation. The same nanostructures were further tested with the simulated sulfide wastewater and the optimized catalyst showed H2 production of 350 mL h-1. The experimental results of time-on stream and catalytic stability demonstrated that ZnS/NiO hierarchical core-shell nanostructures can be recyclable and reusable for the continuous photocatalytic H2 generation.

Enhanced Superhydrophobic Performance of BN-MoS2 Heterostructure Prepared via a Rapid, One-Pot Supercritical Fluid Processing.

Fabrication of highly crystalline BN-MoS2 heterostructure with >95% yield was demonstrated using one-pot supercritical fluid processing within 30 min. The existence of 20-50 layers of BN-MoS2 in the prepared heterostructure was confirmed by AFM analysis. The HR-TEM imaging and mapping analysis revealed the well-melded BN and MoS2 nanosheets in the heterostructure. The drastic reduction in XRD line intensities corresponding to the (002) plane and broadening of the peaks for the BN system over MoS2 indicated the effective exfoliation and lateral size reduction in BN nanosheets during SCF processing. Also, the exfoliated MoS2 nanosheets are preferentially exposed rather than BN nanosheets; consequently, the MoS2 nanosheets sturdily covered BN nanosheets in the heterostructure. The exfoliated BN and MoS2 nanosheets with nanoscale roughness make the surface highly hydrophobic in nature. As a result, the BN-MoS2 heterostructure showed superior superhydrophobic performance with high water contact angle of 165.9°, which is much higher than the value reported in the literature.

In-Situ Nanoarchitectonics of Fe/Co LDH over Cobalt-Enriched N-Doped Carbon Cookies as Facile Oxygen Redox Electrocatalysts for High-Rate Rechargeable Zinc-Air Batteries.

The reality of long-term rechargeable and high-performance zinc-air batteries relies majorly on cost-effective and eminent bifunctional electrocatalysts, which can perform both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Herein, we demonstrate a new approach for the synthesis of in-situ-grown layered double hydroxide of iron and cobalt over a cobalt nanoparticle-enriched nitrogen-doped carbon frame (CoL 2:1) by a simple coprecipitation reaction with facile scale-up and explore its electrocatalytic ORR and OER activity for an electrically rechargeable zinc-air battery. Consequently, the developed composite displays excellent ORR and OER activity with an ORR half-wave potential of 0.84 V, a limiting current density of 5.85 mA/cm2, and an OER overpotential of 320 mV with exceptional stability. The outstanding bifunctionality index of the catalyst (ΔE = 0.72 V) inspired us to utilize it as a cathode catalyst in an in-house developed prototype zinc-air battery. The battery could easily supply a specific capacity of 804 mAh/g with a maximum peak power density of 161 mW/cm2. The battery exhibits an attractive charge-discharge profile with a lesser voltage gap of 0.76 V at 10 mA/cm2 with durability for a period of 200 h and a voltage efficiency of 97%, which surpassed the corresponding Pt/C + RuO2-based zinc-air battery. Further, a maximum load of 50 mA/cm2 could easily be sustained during cycling, revealing its outstanding stability. A series-connected two CoL 2:1-based zinc-air batteries effortlessly enlighten a pinwheel fan and LED panel simultaneously, revealing its practicality. The high electrical conductivity and greater specific surface area of Co/N-C and its robust attachment with Fe/Co LDH preserves both active sites, thereby resulting in exceptional performance. Our method is capable of being flexible enough to create various bifunctional Co/N-C-based composite electrodes, opening up a feasible pathway to rechargeable zinc-air batteries with maximum energy density.

Tailoring of High-Valent Sn-Doped Porous Na3V2(PO4)3/C Nanoarchitechtonics: An Ultra High-Rate Cathode for Sodium-Ion Batteries.

NASICON structured Na3V2(PO4)3 (NVP) has captured enormous attention as a potential cathode for next-generation sodium-ion batteries (SIBs), owing to its sturdy crystal structure and high theoretical capacity. Nonetheless, its poor intrinsic electronic conductivity has led to inferior electrochemical performance in terms of rate capability and long cycling performance. To address this problem, a combined strategy is adopted, such as (1) carbon coating and (2) high valent Sn4+ ion doping in the lattice site of vanadium in the NVP cathode. Carbon coating can effectively enhance the surface electronic conductivity, wherein high-valent Sn4+ improves the bulk intrinsic electronic conductivity of the materials. Moreover, Sn is a well-known alloying/dealloying type anode for SIBs; thus, doping of such metal in cathode materials will assume the role of structure stabilizing pillars and establishing high-performing cathode materials. Herein, Na3V2-xSnx(PO4)3/C (denoted as Sn(x)-NVP/C, where x = 0.00, 0.03, 0.05, 0.07, 0.1) were synthesized via sol-gel route, followed by calcination at 800 °C. XRD, Raman, XPS, and electron microscopy data confirmed the high purity of the synthesized cathode. The optimized Sn(0.07)-NVP/C exhibited excellent electrochemical performance in terms of high rate capability and long cycling performance, a high appreciable capacity of 98 mAh g-1 with capacity retention of 85% after 500 cycles. Similarly, at a high current of 20C, it is still able to deliver a stable capacity of 76 mAh g-1 with 85% capacity retention after 3000 cycles. The rate capability study indicates the high current tolerance of Sn(0.07)-NVP/C up to 70 C with a capacity delivery of 55 mAh g-1. It is worth mentioning that CV and EIS analysis for Sn(0.07)-NVP/C cathode displayed minimum voltage polarization and enhanced diffusion coefficient. Moreover, DFT calculation also proved that the electronic and ionic conductivity of NVP is promoted by Sn doping. Hence, the present results demonstrated that Sn(0.07)-NVP/C is considered a promising cathode for sodium-ion battery application.

Synthesis and electrochemical properties of biporous alpha-Fe2O3 superstructures.

Biporous microsphere, flower and concaved cuboctahedrans like alpha-Fe2O3 superstructures have been synthesized by using a new synthetic method. Hydrothermal reaction of ferric chloride with potassium thiocyanate at 200 degrees C yields self-assembled microsphere, flower, and concaved cuboctahedrans like intermediates in ethanol, water:ethanol (1:1) mixed solvent and in water, respectively. These intermediates were further converted into corresponding alpha-Fe2O3 in a thermal decomposition process at 600 degrees C under oxygen atmospheric conditions. The influence of solvent, hydrothermal temperature, and concentration of iron precursors on the intermediate morphology was studied, and the growth mechanism has also been proposed. The synthesized intermediates and alpha-Fe2O3 were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM) and nitrogen adsorption analysis. The FE-SEM results indicated formation of biporous flowerlike morphology. The electrochemical properties of the flowerlike alpha-Fe2O3 electrodes in a Li-ion battery have been investigated. Plausible formation mechanisms of these intermediates were proposed.

Nanoporous Hollow Carbon Spheres Derived from Fullerene Assembly as Electrode Materials for High-Performance Supercapacitors.

The energy storage performances of supercapacitors are expected to be enhanced by the use of nanostructured hierarchically micro/mesoporous hollow carbon materials based on their ultra-high specific surface areas and rapid diffusion of electrolyte ions through the interconnected channels of their mesoporous structures. In this work, we report the electrochemical supercapacitance properties of hollow carbon spheres prepared by high-temperature carbonization of self-assembled fullerene-ethylenediamine hollow spheres (FE-HS). FE-HS, having an average external diameter of 290 nm, an internal diameter of 65 nm, and a wall thickness of 225 nm, were prepared by using the dynamic liquid-liquid interfacial precipitation (DLLIP) method at ambient conditions of temperature and pressure. High temperature carbonization (at 700, 900, and 1100 °C) of the FE-HS yielded nanoporous (micro/mesoporous) hollow carbon spheres with large surface areas (612 to 1616 m2 g-1) and large pore volumes (0.925 to 1.346 cm3 g-1) dependent on the temperature applied. The sample obtained by carbonization of FE-HS at 900 °C (FE-HS_900) displayed optimum surface area and exhibited remarkable electrochemical electrical double-layer capacitance properties in aq. 1 M sulfuric acid due to its well-developed porosity, interconnected pore structure, and large surface area. For a three-electrode cell setup, a specific capacitance of 293 F g-1 at a 1 A g-1 current density, which is approximately 4 times greater than the specific capacitance of the starting material, FE-HS. The symmetric supercapacitor cell was assembled using FE-HS_900 and attained 164 F g-1 at 1 A g-1 with sustained 50% capacitance at 10 A g-1 accompanied by 96% cycle life and 98% coulombic efficiency after 10,000 consecutive charge/discharge cycles. The results demonstrate the excellent potential of these fullerene assemblies in the fabrication of nanoporous carbon materials with the extensive surface areas required for high-performance energy storage supercapacitor applications.

Synthesis and characterization of fullerene nanowhiskers by liquid-liquid interfacial precipitation: influence of C60 solubility.

Fullerene nanowhiskers (FNWs) composed of C(60) fullerene molecules were prepared using the liquid-liquid interfacial precipitation (LLIP) method in the carbon-disulfide (CS(2)) and isopropyl alcohol (IPA) system. The electron microscopic images reveal the formation of non-tubular FNWs. The X-ray diffraction (XRD) pattern studies indicate the presence of fcc crystalline structure and unusual triclinic structure in the FNWs. The selected area electron diffraction pattern (SAED) analysis demonstrates the existence of triclinic and electron beam assisted fcc to tetragonal crystalline phase transformation. The formation of triclinic structure might be validated due to the partial polymerization of FNWs at C(60) saturated CS(2)-IPA interface. The high solubility of C(60) in CS(2) solvent system results in partial polymerization of FNWs. The polymerization of fullerene molecules in the FNWs has been further confirmed using Raman spectroscopy.

2D/2D Nanoarchitectured Nb2C/Ti3C2 MXene Heterointerface for High-Energy Supercapacitors with Sustainable Life Cycle.

Layered 2D/2D heterointerface composites experience interesting properties that greatly stimulate the recent surge in the attention as robust supercapacitor electrode materials, especially the MXene-based 2D/2D heterointerface for its robust energy storage compatibility. This report unveils a synergistically in situ prepared 2D/2D Nb2C/Ti3C2 MXene (NCTC) heterointerface nanoarchitecture by facile one-pot chemical etching. The methodology adopted enables the interconnected and simultaneous growth of MXenes exposing and retaining their active surfaces for enhanced ion diffusion pathways, charge storage dynamics, microstructural stability, and a noticeable potential window. Henceforth, the in situ developed NCTC heterointerface electrode delivered an excellent specific capacitance of 584 F/g at 2 A/g with a commendable energy density of 38.5 W h/kg in MXene supercapacitors owing to the augmented surface- and redox-based charge storage at the interface. Finally, the developed all-solid-state system demonstrated a superior cycling retention of 98% capacitance after 50,000 cycles. These superlative results encourage the exploration of such prospective 2D/2D heterointerfaces with intriguing charge storage and microstructural attributes for designing next-generation energy storage systems.

Biochar for Supercapacitor Application: A Comparative Study.

Biochar is a carbon-rich solid that can be prepared through heat treatment of biomass under an inert atmosphere. In the present work, biochar prepared from different feedstocks, namely, Litchi chinensis (Litchi) seeds, Syzygium cumini (Jamun) seeds, and pine cone, were evaluated for charge storage in the form of supercapacitors. The physicochemical and electrochemical properties of the biochar were highly dependent on the preparation temperature and the choice of feedstock. Among the three feedstocks, Litchi seed-derived biochar showed the highest specific capacitance of 190 F g-1 at 1 A g-1 in a symmetric cell configuration. N and O heteroatom functionalities in the Litchi seed-derived biochar, higher specific surface area, and pore volume for electrolyte adsorption were responsible for its superior capacitive performance as compared to Jamun seeds and pine cone biochar.

Dual heteroatoms doped SBA-15 templated porous carbon for symmetric supercapacitor in dual redox additive electrolyte.

Porous carbon (PC) based materials is a proficient impetus for upgrading supercapacitor thanks to its traits of high surface area, meso, micropores, and replication morphology. Mainly, single and dual heteroatom doping in PC material is one of the amazing strategies for enhancing the supercapacitor activity due to the interaction of carbon and heteroatom material along with the excessive contribution of by functional groups. Here, we have synthesized nitrogen (N) and boron (B) dual doped PC (NBPC) with the assistance of Santa Barbara Amorphous (SBA-15) silica material and afterward investigated their doping impact of the heteroatom which is investigated for supercapacitor application. Among all, NBPC material delivered a high specific capacitance of 375 F/g at 2 A/g current density in 1 M H2SO4 electrolyte with excellent rate capability and capacitance retention. Such an attractive property of NBPC is a reflection of its high specific surface area (809 m2/g) rendered by N and B functional groups. In addition, the introduction of dual redox additive materials to the electrolyte synergistically enhanced the specific capacity of the symmetric supercapacitor cell. An unprecedented high specific capacity of 929 C/g at 3 A/g current density is observed and a 56% of initial specific capacity was retained when current density increased to 20 A/g. The fabricated symmetric cell using NBPC electrode in 1 M H2SO4 + 0.01 M ammonium metavanadate + Ferrous (II) sulfate dual redox additive electrolyte delivered an energy density of 48.4 W h/kg which is five folds higher than the bare electrolyte (10.1 W h/kg). Similarly, the NBPC electrode delivered a power density of 15 kW/kg in the redox additive electrolyte which is three folds higher than the bare electrolyte (5 kW/kg).

Crumpled B, F Co-doped graphene nanosheets for the fabrication of all-solid-state flexible supercapacitors.

Crumpled B, F co-doped graphene nanosheets (BFGO) have been synthesized using supercritical water as the solvent in a short reaction time of 1 h and were demonstrated for the fabrication of all-solid-state flexible supercapacitors (ASFS). As-synthesized BFGO delivered high specific capacitance with an NaVO3/H2SO4 electrolyte (832 F g-1). Moreover, the fabricated ASFS showed excellent energy and power densities of 24 W h kg-1 and 800 W kg-1 at 1 A g-1, respectively.

Switching the solubility of electroactive ionic liquids for designing high energy supercapacitor and low potential biosensor.

Ionic liquids are regarded as one of the most prodigious materials for sustainable technological developments with superior performance and versatility. Hence, in this study, we have reported the design and synthesis of electroactive disubstituted ferrocenyl ionic liquids (Fc-ILs) with two different counter anions and demonstrated the significance of their anion tuneable physicochemical characteristics towards multifunctional electrochemical applications. The Fc-IL synthesized with chloride counter anion (Fc-Cl-IL) displays water-solubility and can be used as a redox additive in the fabrication of supercapacitor. Supercapacitor device with Fc-Cl-IL based redox electrolyte exhibits outstanding energy and power densities of 91 Wh kg-1 and 20.3 kW kg-1, respectively. Meanwhile, ferrocenyl IL synthesized with perchlorate anion (Fc-ClO4-IL) exhibits water-insolubility and can serve as a redox mediator towards construction of a glucose biosensor. The biosensor comprising Fc-ClO4-IL is able to detect glucose at an exceptionally lower potential of 0.2 V, with remarkable sensitivity and selectivity. This study implies that the introduction of electroactive ILs could afford supercapacitor devices with high energy and power densities and biosensors with less detection potential.

Monodispersed core/shell nanospheres of ZnS/NiO with enhanced H2 generation and quantum efficiency at versatile photocatalytic conditions.

This investigation is first to elucidate the synthesis of mono-dispersed ZnS/NiO-core/shell nanostructures with a uniform thin layer of NiO-shell on the ZnS-nanospheres as a core under controlled thermal treatments. NiO-shell thickness varied to 8.2, 12.4, 18.2, and 24.2 nm, while the ZnS-core diameter remained stable about 96 ± 6 nm. The crystalline phase and core/shell structure of the materials were confirmed using XRD and HRTEM techniques, respectively. Optical properties through UV-vis spectroscopy analysis revealed the manifestation of red-shift in the absorption spectrum of core/shell materials, while the XPS analysis of elements elucidated their stable oxidation states in ZnS/NiO core/shell structure. The optimized ZnS/NiO-core/shell showed 1.42 times higher H2 generation (162.1 mmol h-1 g-1cat) than the pristine ZnS-core (113.2 mmol h-1 g-1cat), and 64.5 times higher than the pristine NiO-shell (2.5 mmol h-1 g-1cat). The quantum efficiency at wavelengths of 420, 365 nm, and 1.5 G air mass filters was found to be 13.5%, 25.0%, and 45.3%, respectively. Water splitting experiments was also performed without addition of any additives, which showed enhanced H2 gas evolution of 1.6 mmol h-1 g-1cat under the sunlight illumination. Photoelectrochemical measurements revealed the stable photocurrent density and minimized charge recombination in the system. The performed recyclability and reusability tests for five recycles demonstrated the excellent stability of the developed photocatalysts.

Metal chalcogenide-based core/shell photocatalysts for solar hydrogen production: Recent advances, properties and technology challenges.

Metal chalcogenides play a vital role in the conversion of solar energy into hydrogen fuel. Hydrogen fuel technology can possibly tackle the future energy crises by replacing carbon fuels such as petroleum, diesel and kerosene, owning to zero emission carbon-free gas and eco-friendliness. Metal chalcogenides are classified into narrow band gap (CdS, Cu2S, Bi2S3, MoS2, CdSe and MoSe2) materials and wide band gap materials (ZnS, ZnSe and ZnTe). Composites of these materials are fabricated with different architectures in which core-shell is one of the unique composites that drastically improve the photo-excitons separation, where chalcogenides in the core can be well protected for sustainable uses. Thus,the core-shell structures promote the design and fabrication of composites with the required characteristics. Interestingly, the metal chalcogenides as a core-shell photocatalyst can be classified into type-I, reverse type-I, type-II and S-type nanocomposites, which can effectively influence and significantly enhance the rate of hydrogen production. In this direction, this review is undertaken to provide a comprehensive overview of the advanced preparation processes, properties of metal chalcogenides, and in particular, photocatalytic performance of the metal chalcogenides as a core-shell photocatalysts for solar hydrogen production.

Open-mouthed metallic microcapsules: exploring performance improvements at agglomeration-free interiors.

Although artificial capsule structures have been thoroughly investigated, functionality at the surfaces of their interiors has been surprisingly overlooked. In order to exploit this aspect of capsular structure, we here report the breakthrough fabrication of metallic (platinum) microcapsules with sufficient accessibility and electroactivity at both interior and exterior surfaces (open-mouthed platinum microcapsules), and also we demonstrate improvements in electrochemical and catalytic functions to emphasize the practical importance of our concept. The open-mouthed platinum microcapsules were prepared by template synthesis using polystyrene spheres, where surface-fused crystalline nanoparticles formed a capsule shell. Subsequent removal of the polystyrene spheres induced formation of mouth-like openings. The open-mouthed platinum microcapsules exhibit a substantial increase of their electrode capability for methanol oxidation and catalytic activities for carbon monoxide (CO) oxidation. Notably, activity loss during CO oxidation due to undesirable particle agglomeration can be drastically suppressed using the open-mouthed microcapsules.

New Method for the Synthesis of 2D Vanadium Nitride (MXene) and Its Application as a Supercapacitor Electrode.

MXenes are the class of two-dimensional transition metal carbides and nitrides that exhibit unique properties and are used in a multitude of applications such as biosensors, water purification, electromagnetic interference shielding, electrocatalysis, supercapacitors, and so forth. Carbide-based MXenes are being widely explored, whereas investigations on nitride-based ones are seldom. Among the nitride-based MXenes obtained from their MAX phases, only Ti4N3 and Ti2N are reported so far. Herein, we report a novel synthesis of V2NT x (T x is the surface termination) obtained by the selective removal of "Al" from V2AlN by immersing powders of V2AlN in the LiF-HCl mixture (salt-acid etching) followed by sonication to obtain V2NT x (T x = -F, -O) MXene which is then delaminated using the dimethyl sulfoxide solvent. The V2NT x MXene is characterized by X-ray diffraction studies, field emission scanning electron microscope imaging, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscope imaging. Supercapacitor electrodes are prepared using V2NT x MXenes and their electrochemical performances are examined by cyclic voltammetry, galvanostatic charge/discharge measurement, and electrochemical impedance spectroscopy. The V2NT x MXene electrode exhibits a specific capacitance of 112.8 F/g at a current density of 1.85 mA/cm2 with an energy and power density of 15.66 W h/kg and 3748.4 W/kg, respectively, in 3.5 M KOH aqueous electrolyte. The electrode exhibits an excellent capacitance retention of 96% even after 10,000 charge/discharge cycles. An asymmetric supercapacitor fabricated with V2NT x as a negative electrode and Mn3O4 nanowalls as a positive electrode helps obtain a cell voltage of 1.8 V in aqueous KOH electrolyte.

Solvent engineering for shape-shifter pure fullerene (C60).

As a highly anticipated technique for bottom-up nanotechnology, i.e., shape control of pure functional molecules, we here report controlled formation of two-dimensional (2D) objects such as hexagons and rhombi and their selective shape shifting into one-dimensional (1D) rods through solvent-dependent changes of crystal lattice, all from pure C(60). Uniformly shaped rhombi and hexagons were obtained at tert-butyl alcohol/toluene and i-propyl alcohol/CCl(4) interfaces, respectively. In addition, exposure of these 2D nanosheets to water induced selective transformation into 1D nanorods. Nanorhombi were converted to short nanorods upon exposure to water. This shape shift is accompanied by changes in crystalline structures from a mixed fcc/hexagonal to pure fcc lattice, the latter of which is almost identical with morphologically similar C(60) nanowhiskers. Metastable nanorhombi which possess a strained mixed crystalline structure metamorphosize into the more stable short nanowhisker (nanorods). In contrast, the stable nanohexagon of a single lattice (and so less strain) does not undergo shape shifting. These results clearly demonstrate controlled formation of 2D nanosheets with various shapes (hexagons, rhombi, etc.) and selective shape shifting to nanorods (short nanowhiskers) all from pure C(60) molecules by very simple solvent treatments.

Preparation and optical properties of fullerene/ferrocene hybrid hexagonal nanosheets and large-scale production of fullerene hexagonal nanosheets.

The supramolecular nanoarchitectures, C(60)/ferrocene nanosheets, were prepared by a simple liquid-liquid interfacial precipitation method and fully characterized by means of SEM, STEM, HRTEM, XRD, Raman and UV-vis-NIR spectra. The highly crystallized C(60)/ferrocene hexagonal nanosheets had a size of ca. 9 microm and the formulation C(60)(ferrocene)(2). A strong charge-transfer (CT) band between ferrocene and C(60) was observed at 782 nm, indicating the presence of donor-acceptor interaction in the nanosheets. Upon heating the nanosheets to 150 degrees C, the CT band disappeared due to the sublimation of ferrocene from the C(60)/ferrocene hybrid, and C(60) nanosheets with an fcc crystal structure and the same shape and size as the C(60)/ferrocene nanosheets were obtained.

Supercritical water assisted preparation of recyclable gold nanoparticles and their catalytic utility in cross-coupling reactions under sustainable conditions.

Preparation of gold nanoparticles (AuNPs) in environmentally friendly water without using any reducing agents under supercritical conditions is demonstrated. PXRD, XPS, FE-SEM and HR-TEM analysis confirmed the formation of phase-pure and crystalline AuNPs of the size of ∼10-30 nm. The catalytic potential of AuNPs was manifested through a generalized green procedure that could accommodate both Sonogashira as well as Suzuki coupling under aqueous conditions at low catalytic loading (0.1 mol%). The AuNP catalyst was found to be recuperated after the reaction and reused for up to six catalytic cycles with no leaching out of gold species as confirmed through ICP-OES analysis. With no confinement of AuNP catalysis to cross-coupling reaction, synthetic extension to one-flask preparation of π-conjugated semiconductors (4 examples) and their optoelectronic properties were also investigated. Other significant features of the present work include short reaction time, site-selectivity, wide substrate scope, high conversion, good chemical yields and applicability in gram-scale synthesis. Overall, the results of this paper signify an operationally sustainable supercritical fluid processing method for the synthesis of AuNPs and their catalytic application towards cross-coupling reactions in green media.