Template-free Approach Research Articles

Enhanced hydrogen evolution reaction on highly stable titania‐supported PdO and Eu2O3nanocomposites in a strong alkaline solution

In this work, PdO/TiO2 and Eu2O3/TiO2 nanocomposites (NCs) were synthesized using a new facile, template-free, and one-step solvothermal approach and characterized by several instrumentation techniques. X-ray photoelectron spectroscopy studies revealed the presence of oxidized form of the Pd and Eu nanoparticles within the NC materials (PdO and Eu2O3). The two catalysts exhibited remarkable activity for the hydrogen evaluation reaction (HER) in a strong alkaline solution (4.0 M NaOH) with PdO/TiO2 catalyst being the best, which recorded an exchange current density (jo) of 0.26 mA cm−2 and a Tafel slope (βc) of 125 mV dec−1. Such parameters are not far from those recorded for a commercial Pt/C catalyst (0.71 mA cm−2 and 120 mV dec−1) performed here under the same operating conditions. Eu2O3/TiO2 catalyst recorded jo and βc values of 0.05 mA cm−2 and 135 mV dec−1. The Tafel slopes 125 and 135 mV dec−1 calculated on the PdO/TiO2 and Eu2O3/TiO2 catalysts suggest a HER kinetics controlled by the Volmer step. PdO/TiO2 catalyzed the HER with a high turnover frequency of 2.3 H2/s at 0.2 V versus the reversible hydrogen electrode, while Eu2O3/TiO2 catalyst only measured a turnover frequency value of 1.25 H2/s at the same overpotential. The two catalysts exhibited excellent stability and durability after 10 000 cycles and 72 hours of controlled potential electrolysis at a high cathodic overpotential, reflecting their practical applicability. Scanning electron microscope and X-ray photoelectron spectroscopy examinations revealed that the morphology and chemistry of both catalysts were not altered as a result of the performed long-term stability and durability tests.

Rational synthesis of one-dimensional carbon nitride-based nanofibers atomically doped with Au/Pd for efficient carbon monoxide oxidation

Controlled synthesis of carbon nitride nanostructures doped with noble metal-based catalysts is important in various catalytic applications. Herein, we developed a scalable, facile, and template-free approach for one-pot synthesis of one-dimensional gC3N4 nanofibers co-doped with Au and Pd donated as (Au/Pd/gC3N4NFs). The developed method tailored the high mass production of uniform gC3N4 nanofibers with a great surface area of (85 m2 g−1) and coherently co-doped with Au and Pd. Intriguingly, the complete CO oxidation temperature of Au/Pd/gC3N4NFs (144 °C) is significantly lower than that of Pd/gC3N4NFs (191 °C) and Au/gC3N4NFs (205 °C). The superior activity of Au/Pd/gC3N4NFs is attributed to the combination between outstanding inherent catalytic merits of Au/Pd and the unique physicochemical properties of gC3N4 nanofibers. Our newly designed simple approach may open the way for utilization of gC3N4 nanofibers in CO oxidation reaction.

Template-Free Synthesis of Chemically Asymmetric Silica Nanotubes for Selective Cargo Loading and Sustained Drug Release

SiO2 nanotubes (NTs), with uniform diameter (∼25 nm) and tailored shell thickness (1–5 nm), and featuring chemically asymmetric surfaces (a silane-functionalized exterior surface and a negatively charged (−Si–O–) interior surface) are prepared by a facile, template-free approach. Owing to their chemically asymmetric properties, positively charged cargoes can be selectively loaded with high content into the SiO2 NTs via electrostatic interaction. Mediated by polyamidoamine dendrimers preassembled in the NTs, different noble metal nanoparticles can be selectively deposited inside the NTs with high density and uniform size. Owing to their high specific surface area and elongated pore structure with lengths up to several micrometers, the SiO2 NTs exhibit a high loading capacity (80 wt %) for positively charged therapeutic agents, which exhibit sustained cargo release properties on the order of several months if the NTs are assembled into a membrane structure.

Porous size dependent g-C3N4 for efficient photocatalysts: Regulation synthesizes and physical mechanism

We propose a new template-free approach for the synthesis of porous graphitic carbon nitride (g-C3N4) nanosheets as efficient photocatalysts. This new template-free method includes a one-step hydrothermal treatment and a sequential two-step thermal treatment. This method can provide massively porous g-C3N4 nanosheets without external physical defects (such as atom doping and/or atom vacancies) in the g-C3N4 nanosheets. The Brunauer-Emmett-Teller (BET) surface areas and pore volumes of the porous g-C3N4 nanosheets can reach 125 m2 g-1 and 1.2 cm3 g-1, respectively, thereby showing significant increases of 22 and 15 times, respectively, compared with those of the pristine g-C3N4 nanosheets. The synthesized porous g-C3N4 nanosheets have large specific surface areas and exhibit high photocatalytic activities that are enhanced by as much as 8 times compared to those of the pristine g-C3N4 for the photodegradation of gas pollutants (using the photocatalysis of 2-propanol to acetone as an example) under visible light (λ > 420 nm). Experimental and theoretical results reveal the suitable porous size of porous g-C3N4 plays essential role for the efficient photocatalysis. Our multistep template-free approach can provide a new method for the preparation of porous g-C3N4 nanosheets as efficient photocatalysts that are better than those obtained by destroying the physical structures of the pristine g-C3N4 nanosheets.

Solution Self-Assembly of an Alternating Copolymer toward Hollow Carbon Nanospheres with Uniform Micropores.

Controllable preparation of porous hollow carbon spheres (HCSs) has attracted considerable attention due to their potential applications, e.g., in energy conversion and storage. We report for the first time the synthesis of narrowly size-distributed HCSs with uniform micropores in the wall, through a simple template-free approach, which employs the solution self-assembly of an alternating copolymer (poly(9,9'-bis(4-glycidyloxyphenyl)fluorene-alt-2,3-dihydroxy-butylene dithioether) (P(BGF-a-DHBDT))). This alternating copolymer first self-assembled into previously undocumented hollow polymeric spheres (HPSs) in an N,N-dimethylformamide (DMF)/H2O solvent mixture. After the cross-linking of the BGF segments in the spheres, the stabilized HPSs (CL-HPSs) were carbonized at 800 °C under N2 atmosphere, yielding porous HCSs with uniform micropores of very narrow size distribution (0.4-0.8 nm) in the wall, benefiting from the uniform DHBDT block length in the alternating copolymer. Through KOH activation, which made the internal pores fully interconnected, uniform micropores (0.5-1.0 nm) of a narrow size distribution were retained within the activated HCSs (A-HCSs), while their specific surface areas (SSAs) were much increased to 2580 m2 g-1. As a proof of concept, the A-HCSs were applied as electrode materials of supercapacitors. They exhibited superior electrochemical performance with a high specific capacitance (292 F g-1 at 0.2 A g-1), good rate capability, and outstanding cycling stability with no apparent capacitance loss after 10 000 cycles.

Template-Free, Self-Doped Approach to Porous Carbon Spheres with High N/O Contents for High-Performance Supercapacitors

A template-free and self-doping approach is developed for fabricating N,O-enriched porous carbon spheres (PCSs) via direct carbonization/activation of melamine-glyoxal polymer. The interconnected spherical morphology of PCSs generates stacking porosities as ion reservoirs for rapid ion diffusion and affords conductive networks to shorten the transport lengths for electron transfer. Besides, PCSs exhibit a large surface area (1302 m2 g–1), ample ultramicropores (0.54 nm), and developed supermicro- and mesopores. This unique pore architecture provides optimized ion-accessible pore size to enhance double layer capacitance, and serves as ion-highways for rapid diffusion of electrolyte ions. Furthermore, high N/O elements (7.97/10.16 wt %) incorporated into PCSs improve surface wettability and supply additional pseudocapacitance. Therefore, the resultant PCS electrodes exhibit superior electrochemical performances, such as a high specific capacitance up to 344 F g–1 at 1.0 A g–1, remarkable rate capability, an...

A facile one-pot synthesis of CaO/CuO hollow microspheres featuring highly porous shells for enhanced CO2 capture in a combined Ca–Cu looping process via a template-free synthesis approach

The preparation of CaO/CuO composites with high performance is essential for combined Ca–Cu looping process, where the exothermic reduction of CuO with methane is used in situ to calcine CaCO3.

Thiophene containing microporous and mesoporous nanoplates for separation of mercury from aqueous solution

Thiophene-based novel porous polymeric nanoplates synthesized through a template free approach show high mercury capture efficiency from contaminated water and may be promising for environmental applications.

Improved charging and strain rates by laser perforating polypyrrole actuator electrodes

Conducting polymer actuators generate significant strains (1%–10%) when driven at low voltages, and are muscle-like in their linear deformation, mechanical compliance, silent operation, and energy density. However, slow electrochemical processes have hindered widespread application. To operate electroactive polymer actuators in practical applications such as soft robotics, the speed of energy delivery is often important. Recent work has achieved very fast actuation by using very thin films and blending of materials of high ionic conductivity with conducting polymers, allowing fast insertion of ions. Here we make microscopic arrays of holes in relatively thick, easy to handle conducting polymer films in order to speed ion insertion and actuation. A single-step, top-down, non-contact and template-free approach is used, employing femto and picosecond lasers to texturize polypyrrole based actuators while preserving the stress and strain output. A wide range of hole separations and diameters (pitch/diameter from 9.75/5.17 μm to 24.7/13.2 μm) are explored to reduce the ion diffusion path length in the bulk polymer. This led to a speed increase of between 2 and 30 times. A finite element model based on diffusion shows similar improvements, suggesting that the reduced distance of mass transport achieved by laser perforation is the key to faster response times in the thick electrodes used. The demonstrated ability to increase rate of response using micromachined electrodes is potentially applicable to batteries and supercapacitors.

Hierarchical porous zeolitic imidazolate frameworks nanoparticles for efficient adsorption of rare-earth elements

Hierarchical porous zeolitic imidazolate frameworks nanoparticles (ZIF-8 NPs) were synthesized at room temperature via a template-free approach under dynamic conditions (stirring) using water as a ...

High-Performance Flexible In-Plane Micro-Supercapacitors Based on Vertically Aligned CuSe@Ni(OH)2 Hybrid Nanosheet Films.

The orientation and hybridization of ultrathin two-dimensional (2D) nanostructures on interdigital electrodes is vital for developing high-performance flexible in-plane micro-supercapacitors (MSCs). Despite great progress has been achieved, integrating CuSe and Ni(OH)2 nanosheets to generate advanced nanohybrids with oriented arrangement of each component and formation of porous frameworks remains a challenge, and their application for in-plane MSCs has not been explored. Herein, the vertically aligned CuSe@Ni(OH)2 hybrid nanosheet films with hierarchical open channels are skillfully deposited on Au interdigital electrodes/polyethylene terephthalate substrate via a template-free sequential electrodeposition approach, and directly employed to construct in-plane MSCs by choosing polyvinyl alcohol-LiCl gel as both the separator and the solid electrolyte. Because of the unique geometrical structure and combination of intrinsically conductive CuSe and battery-type Ni(OH)2 components, such hybrid nanosheet films can not only resolve the poor conductivity and re-stacking problems of Ni(OH)2 nanosheets but also create the 3D electrons or ions transport pathway. Thus, the in-plane MSCs device fabricated by such hybrid nanosheet films exhibits high volumetric specific capacitance (38.9 F cm-3). Moreover, its maximal energy and power density can reach 5.4 mW h cm-3 and 833.2 mW cm-3, superior to pure CuSe nanosheets, and most of reported carbon materials and metal hydroxides/oxides/sulfides based in-plane MSCs ones. Also, the hybrid nanosheet films device shows excellent cycling performance, good flexibility, and mechanical stability. This work may shed some light on optimizing 2D electrode materials and promote the development of flexible in-plane MSCs or other energy storage systems.

Untemplated Resveratrol-Mediated Polydopamine Nanocapsule Formation.

Nanocapsules can be designed for applications including drug delivery, catalysis, and biological imaging. The mussel-inspired material polydopamine is a promising shell layer for nanocapsules because of its free radical scavenging capacity, ability to react with a broad range of functional molecules, lack of toxicity, and biodegradability. Previous reports of polydopamine nanocapsule formation have relied on a templating approach. Herein, we report a template-free approach to polydopamine nanocapsule formation in the presence of resveratrol, a naturally occurring anti-inflammatory and antioxidant compound found in red wine and grapes. Synthesis of nanocapsules occurs spontaneously in an ethanolic resveratrol/dopamine·HCl solution at pH 8.5. UV-vis absorbance spectroscopy and X-ray photoelectron spectroscopy indicate that resveratrol is incorporated into the nanocapsules. We also observed the formation of a soluble fluorescent dopamine-resveratrol adduct during synthesis, which was identified by high-performance liquid chromatography, UV-vis spectroscopy, and electrospray ionization mass spectrometry. Using transmission electron microscopy and dynamic light scattering, we studied the influence of solvent composition, dopamine concentration, and resveratrol/dopamine ratio on the nanocapsule diameter and shell thickness. The resulting nanocapsules have excellent free radical scavenging activity as measured by a 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay. Our work provides a convenient pathway by which resveratrol, and possibly other hydrophobic bioactive compounds, may be encapsulated within polydopamine nanocapsules.

Template-free 2D particle fusion in localization microscopy.

Methods that fuse multiple localization microscopy images of a single structure can improve signal-to-noise ratio and resolution, but they generally suffer from template bias or sensitivity to registration errors. We present a template-free particle-fusion approach based on an all-to-all registration that provides robustness against individual misregistrations and underlabeling. We achieved 3.3-nm Fourier ring correlation (FRC) image resolution by fusing 383 DNA origami nanostructures with 80% labeling density, and 5.0-nm resolution for structures with 30% labeling density.

Cathodically activated Au/TiO2 nanocomposite synthesized by a new facile solvothermal method: An efficient electrocatalyst with Pt-like activity for hydrogen generation

We report here a facile, template-free and one-step solvothermal approach for the synthesis of high-temperature stable gold/titania nanocomposite (NCs), providing a new, simple, quick and inexpensive wet-chemical route. Our approach is based on the assembly of gold salt and titanium butoxide in dimethyl sulfoxide (DMSO). Also, we present here, for the first time, a cathodically activated Au/TiO2 catalyst with Pt/C activity for the hydrogen evolution reaction (HER) in 0.5 M H2SO4 in the dark. The as-prepared (unactivated) Au/TiO2 NCs exhibits considerable electrocatalytic activity for H2 generation in the dark, with a low onset potential (EHER) of −64 mV vs. RHE, a Tafel slope (-bc) of 60 mV dec−1 and an exchange current density (jo) of 0.12 mA cm−2. Long-term stability and durability tests in 0.5 M H2SO4, employing cyclic voltammetry technique (10,000 of repetitive cycling) and 72 h of chronoamperometry measurements at a high cathodic potential (cathodic activation), reveal that the electrocatalyst activates during such aging processes yielding an activated Au/TiO2 catalyst with Pt/C-like activity for H2 generation (EHER -3 mV, -bc: 35 mV dec−1, and jo: 0.95 mA cm−2). The outstanding HER activity of the activated catalyst is discussed.

Cu doped cubic pyrite-type CoS2 ball like superstructures as heterogeneous photocatalyst

Copper doped CoS2 superstructures were prepared by template-free hydrothermal approach and characterized by X-ray powder diffraction, scanning electron microscopy, transition electron microscopy, UV-vis and PL spectroscopy. The as-prepared products were assembled to ball like structures at pure CoS2 and plates at doping one (CC-2), both of which were composed of similar cubic structures. Doping Cu into CoS2 lattice resulted in wide light absorption in the visible-range and thus enhancing photocatalytic activity for degradation of RhB. When the amount of doping reached 2mole%, heterogeneous photocatalyst exhibited a higher activity compared with pure one at room and higher temperatures.

Gold nanospirals on colloidal gold nanoparticles

Synthesis of asymmetric nanostructures has always been a great challenge. In particular, there are only limited approaches for growing spiral nanowires in solution, and almost all of them require templates. Here, as a step in advancing the synthetic capability at the nanoscale, we report a wet chemistry template-free approach for growing hybrids spiral gold nanowires. The spiral gold nanowires were grown from the surface of colloidal gold nanoparticles, forming hybrid Au nanostructures. As an application of the active surface growth mechanism, the mechanistic understanding enables systematic adjustment of the nanowire morphology. The length and width of the spiral nanowires could be readily adjusted. Furthermore, the number of spiral nanowire on each Au nanoparticle, could be tuned by the pre-hydrolysis of the surface modification reagent. Such versatile system allows creation of complex nanostructures like the octopus-like and spider-like Au hybrids.

Hierarchical nanoporous activated carbon as potential electrode materials for high performance electrochemical supercapacitor

Abstract Recently, biomass-derived activated carbon nanomaterials represent a potential candidate in achieving sustainable and low-cost energy storage devices. Herein, we report a facile synthesis of hierarchical nanoporous activated carbon (NAC) by template-free and cost effective approach using bio-derived food waste namely “Indian Cake Rusk” (ICR) and its application in high performance supercapacitors for the first time. The influence of carbon activation process over the physicochemical properties, morphological structure, as well as supercapacitive performance was systematically studied. When used as an electrode in a supercapacitor, the as-synthesized NAC material offered a high specific capacitance of 381.0 F g-1 at a current density of 1.7 A g−1 with an impressive 95% capacity retention even after 6000 cycles using 1.0 M H2SO4 electrolyte. The NAC material also furnished a maximum energy density of 47.1 Wh kg−1 and power density of 22644.0 W kg−1 which is higher than the existing carbon based electrode using 1.0 M LiPF6 electrolyte in symmetric supercapacitor. The superior electrochemical performance of NAC material is ascribed to huge BET surface area (1413.0 m2 g−1), hierarchical micro/nanoporosity, and good electrical conductivity which could serve as a promising carbon material for advanced applications in energy, environmental, and biomedical fields.

Facile Preparation of Metal-Organic Framework (MIL-125)/Chitosan Beads for Adsorption of Pb(II) from Aqueous Solutions.

In this study, novel composite titanium-based metal-organic framework (MOF) beads were synthesized from titanium based metal organic framework MIL-125 and chitosan (CS) and used to remove Pb(II) from wastewater. The MIL-125-CS beads were prepared by combining the titanium-based MIL-125 MOF and chitosan using a template-free solvothermal approach under ambient conditions. The surface and elemental properties of these beads were analyzed using scanning electron microscopy, Fourier transform infrared and X-ray photoelectron spectroscopies, as well as thermal gravimetric analysis. Moreover, a series of experiments designed to determine the influences of factors such as initial Pb(II) concentration, pH, reaction time and adsorption temperature was conducted. Notably, it was found that the adsorption of Pb(II) onto the MIL-125-CS beads reached equilibrium in 180 min to a level of 407.50 mg/g at ambient temperature. In addition, kinetic and equilibrium experiments provided data that were fit to the Langmuir isotherm model and pseudo-second-order kinetics. Furthermore, reusability tests showed that MIL-125-CS retained 85% of its Pb(II)-removal capacity after five reuse cycles. All in all, we believe that the developed MIL-125-CS beads are a promising adsorbent material for the remediation of environmental water polluted by heavy metal ions.

Synthesis of Mesoporous Germanium Phosphide Microspheres for High-Performance Lithium-Ion and Sodium-Ion Battery Anodes

Germanium phosphide is a potential anode material because of its high theoretical capacity and incredible rate capability on lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). However, the huge volume change that occurs while germanium phosphide is converted to Na3P or Li3P directly leads to poor cyclability and limits further applications. Herein, mesoporous germanium phosphide (MGePx) microspheres with diameter size ranging from 0.5 to 1.5 μm were first prepared by a one-step and template-free approach. MGePx microspheres were composed of nanoparticles of around 10 nm with a narrow distribution of pore sizes of around 4 nm. The MGePx possessed superior features in LIBs/SIBs since it shortens the diffusion path of the energy carrier and provides the buffer space for the transport of Li/Na ions. MGePx showed attractive electrochemical properties as a potential anode candidate, such as a high first-cycle Coulombic efficiency of 82.63%, high reversible capacity (1400 mA h g–1 after 150 cycles at ...

A Facile and Green Approach to Synthesize Mesoporous Anatase TiO2 Nanomaterials for Efficient Dye-Sensitized and Hole-Conductor-Free Perovskite Solar Cells

Mesoporous anatase TiO2 nanomaterials (MATNs) with both large specific surface areas and structural coherence are highly desirable to achieve excellent physicochemical properties for photovoltaic applications, but the existing synthesis methods either need templates or cause pollution. Herein we report a simple, template-free, and green approach to synthesize MATNs consisting of interconnected nanoparticles. The Ti-complex intermediates were first prepared using titanium isopropoxide and acetic acid in a solvothermal reaction, which went through a morphology transformation sequence of nanowires, microspheres, and microflowers with a prolonged reaction time. Then the Ti-complex intermediates were cracked into MATNs under annealing, which were applied in dye-sensitized solar cells (DSSCs) and hole-conductor-free perovskite solar cells (HPSCs). The mesoporous anatase TiO2 nanowire-based DSSCs achieved a high power conversion efficiency (PCE) up to 7.78% because of both a high dye-adsorption capacity and long...