Template-free Approach Research Articles

Unveiling One-Pot Template-Free Fabrication of Exquisite Multidimensional PtNi Multicube Nanoarchitectonics for the Efficient Electrochemical Oxidation of Ethanol and Methanol with a Great Tolerance for CO.

Multidimensional bimetallic Pt-based nanoarchitectonics are highly promising in electrochemical energy conversion technologies because of their fancy structural merits and accessible active sites; however, hitherto their precise template-free fabrication remains a great challenge. We report a template-free solvothermal one-pot approach for the rational design of cocentric PtNi multicube nanoarchitectonics via adjusting the oleylamine/oleic acid ratio with curcumin. The obtained multidimensional PtNi multicubes comprise multiple small interlace-stacked nanocube subunits assembled in spatially porous branched nanoarchitectonics and bound by high-index facets. The synthetic mechanism is driven by spontaneous isolation among prompt nucleation and oriented attachment epitaxial growth. These inimitable architectural and compositional merits of PtNi multicubes endowed the ethanol oxidation mass and specific activity by 5.6 and 9.03 times than the Pt/C catalyst, respectively, along with the enhancement of methanol oxidation mass activity by 2.3 times. Moreover, PtNi multicubes showed superior durability and a higher tolerance for CO poisoning than the Pt/C catalyst. This work may pave the way for tailored preparation of Pt-based nanoarchitectonics for myriad catalytic reactions.

Integration of mesoporous ZnO and Au@ZnO nanospheres into sensing device for the ultrasensitive CH3COCH3 detection down to ppb levels

Surface modification of metal oxide nanostructures with noble metals has attracted significant attention of researchers because of their importance in gas sensing applications. In this regard, mesoporous zinc oxide nanospheres (ZnO NSs) were designed through a simple template-free solvothermal approach and successive anchoring of gold nanoparticles (Au NPs) onto it was achieved through a chemical process followed by thermal treatment. The synergistic effects of different Au NPs loadings onto the structure, surface morphology, element contents, as well as chemiresistive gas sensing activities of solvothermal-mediated ZnO NSs were examined thoroughly and discussed. Gas sensing studies demonstrated that the sensor based on Au@ZnO-3 NSs exhibits excellent acetone (CH3COCH3) sensing characteristics (Response = 194) compared to pristine ZnO NSs sensor (Response = 2.86) at a lower temperature of 170 °C. Besides, Au@ZnO NSs sensor is able to detect CH3COCH3 concentration down to ppb-levels (500 ppb) with excellent response repeatability. Observed CH3COCH3 sensing performances of all the Au loaded ZnO NSs sensors were found to be almost 50 times higher than pristine ZnO NSs sensor. Such an excellent CH3COCH3 sensing performance of Au@ZnO NSs is mainly credited to the catalytic activity of Au NPs and the strong metal-semiconductor contacts between Au NPs and ZnO NSs.

Metal–organic framework-derived ZnMoO4 nanosheet arrays for advanced asymmetric supercapacitors

A metal–organic framework (MOF)-derived ZnMoO4 nanosheets architecture is synthesized on Ni foam using a facile and rapid template-free microwave-assisted hydrothermal approach and subsequent calcination. Further characterizations show that this binder-free electrode is composed of ZnMoO4 nanosheet arrays and, therefore, exhibits an excellent electrochemical performance. The nanosheet array-assembled 3D-frameworks exhibit a maximum-specific capacitance of 1212 F g−1 at a current density of 1 A g−1, and a good rate capability with a capacitance of 523 F g−1 even at a high current density of 20 A g−1. Approximately, 93.5% of the maximum-specific capacity is retained, even after 5000 continuous charge–discharge cycles, which exceeds most of ZnMoO4 and ZnMoO4-based electrodes reported so far. A ZnMoO4@Ni foam//GA hybrid device exhibits a maximum-specific capacity of 89 F g−1 at a current density of 1 A g−1, along with a substantial specific energy of 31.8 W h kg−1 at a specific power of 920 W kg−1. These results confirmed that the MOF-derived binder-free ZnMoO4 nanosheet arrays are suitable positive electrode materials for hybrid supercapacitors. Our work demonstrates an improved step toward rational design of high-performance integrated electrodes for supercapacitors with a new vision for theoretical and practical applications.

A robust, template-free approach to precise radial velocity extraction

ABSTRACT Doppler spectroscopy is a powerful tool for discovering and characterizing exoplanets. For decades, the standard approach to extracting radial velocities (RVs) has been to cross-correlate observed spectra with a weighted template mask. While still widely used, this approach is known to suffer numerous drawbacks, and so in recent years increasing attention has been paid to developing new and improved ways of extracting RVs. In this proof-of-concept paper, we present a simple yet powerful approach to RV extraction. We use Gaussian processes to model and align all pairs of spectra with each other; we combine the pairwise RVs thus obtained to produce accurate differential stellar RVs, without constructing any template. Doing this on a highly localized basis enables a data-driven approach to identifying and mitigating spectral contamination, even without the input of any prior astrophysical knowledge. We show that a crude implementation of this method applied to an inactive standard star yields RVs with comparable precision to and significantly lower rms variation than RVs from industry-standard pipelines. Though amenable to numerous improvements, even in its basic form presented here our method could facilitate the study of smaller planets around a wider variety of stars than has previously been possible.

Polyoxotungstate ([PW11O39]7-) immobilized on mesoporous polymer for selective liquid-phase oxidation of alcohols using H2O2.

Selective oxidation of alcohols is an attractive organic transformation and has received tremendous attention from the scientific community over the years. Herein, a mesoporous polymer (MP) was synthesized by a template-free solvothermal approach. The surface of the MP was functionalized with quaternary ammonium groups and polyoxotungstate anion (PW11O397−) was subsequently supported on the MP as a counter anion to the ammonium cation by a simple ion-exchange procedure. The structure of PW11 and PW4 complexes was confirmed by 31P NMR and FTIR analysis. The surface properties of all the catalysts synthesized were explored by various characterization techniques such as nitrogen sorption, TGA, contact angle measurement, and ICP-OES analysis. The synthesized PW11/MP catalysts were employed for selective oxidation of alcohols. Among the various PW11 supported catalysts, PW11/MP (80 : 20) demonstrated excellent catalytic activity for the oxidation of alcohols using aqueous H2O2. The PW11/MP (80 : 20) catalyst showed good catalytic activity for oxidation of a wide range of alcohols including substituted, heterocyclic and secondary alcohols. The superior catalytic activity of PW11/MP (80 : 20) is attributed to an optimum balance in the hydrophilicity/hydrophobicity in the mesoporous environment, better catalyst wettability, and enrichment of reactants in the catalytic active sites.

One-pot synthesis of template-free hollow anisotropic CaCO3 structures: towards inorganic shape-mimicking drug delivery systems.

A major obstacle in the introduction of nanoformulated drugs has been the fact that the shape of the drug delivery systems (DDSs) - the most important parameter driven by the nature of viruses and bacteria - remains almost out-of-scope in artificial systems. Here we propose a potential solution for this problem by developing a template-free approach for the formulation of hollow bacteria-like CaCO3-based pH-sensitive DDSs with controllable anisotropy and click-release behavior.

Controlled Synthesis of Pt Doped SnO2 Mesoporous Hollow Nanospheres for Highly Selective and Rapidly Detection of 3-Hydroxy-2-Butanone Biomarker.

Listeria monocytogenes (L. monocytogenes) has been recognized as one of the extremely hazardous and potentially life-threatening food-borne pathogens, its real-time monitoring is of great importance to human health. Herein, a simple and effective method based on platinum sensitized tin dioxide semiconductor gas sensors has been proposed for selective and rapid detection of L. monocytogenes. Pt doped SnO2 nanospheres with particular mesoporous hollow structure have been synthesized successfully through a robust and template-free approach and used for the detection of 3-hydroxy-2-butanone biomarker of L. monocytogenes. The steady crystal structure, unique micromorphology, good monodispersit, and large specific surface area of the obtained materials have been confirmed by X-ray diffraction (XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Brunauer-Emmett-Teller (BET), and Photoluminescence spectra (PL). Pt doped SnO2 mesoporous hollow nanosphere sensors reach the maximum response of 3-hydroxy-2-butanone at 250°C. Remarkably, sensors based on SnO2 mesoporous hollow nanospheres with 0.16 wt% Pt dopant exhibit excellent sensitivity (Rair/Rgas = 48.69) and short response/recovery time (11/20 s, respectively) to 10 ppm 3-hydroxy-2-butanone at the optimum working temperature. Moreover, 0.16 wt% Pt doped SnO2 gas sensors also present particularly low limit of detection (LOD = 0.5 ppm), superb long-term stability and prominent selectivity to 3-hydroxy-2-butanone. Such a gas sensor with high sensing performance foresees its tremendous application prospects for accurate and efficient detection of foodborne pathogens for the food security and public health.

Template-free synthesis of uniform hollow silica nanoparticles for controllable antireflection coatings

Antireflection coatings consisting of nanoparticles have promising applications in a wide range of UV optical fields, such as high-power laser systems and space telescopes. However, an open question for these coatings is how to minimize light scattering caused by the nanoparticles. Here, we utilize hollow silica nanoparticles to realize antireflection coatings, which largely diminish light scattering and, hence, exhibit excellent transmission even at UV wavelengths. The hollow silica nanoparticles were synthesized using a template-free approach and then dip coated onto fused silica substrates to form antireflection coatings. The coatings were found to exhibit nearly 100% transmission at any wavelength ranging from the UV to IR bands by variation of the coating thickness. Moreover, the coatings showed relatively high environmental stability because their hollow structures were insensitive to contaminants. This study provides a novel route to fabricate UV antireflection coatings with improved optical properties and good environmental stability, which will help promote the understanding, design and fabrication of optical coatings.

MAPbI3 nanowires prepared by a facile vapor transfer method for simple photodetector

MAPbI3 nanowires have become one of the promising materials for optoelectronic devices. Herein, a simple template-free vapor transfer approach to synthesize MAPbI3 nanowires on various substrates for optoelectronic device developed. High crystalline MAPbI3 nanowires were realized via methyl-ammonium iodide (MAI) vapor transfer treatment with PbI2 nanowires. PbI2 nanowires were prepared by a self-assembled procedure where PbI2 film was recrystallized and converted to nanowires structure with the exposure of dimethylacetamide (DMAC) vapor. On top of that, the density of MAPbI3 nanowires could be modulated by simply tuning the thickness of PbI2 film. The as-fabricated MAPbI3 nanowires photodetector exhibits a satisfying responsivity of 0.115 A W−1 @3 V while the rise time is less than 0.63 s and the decay time is less than 0.73 s. The study presents a bright future of MAPbI3 nanowires for optoelectronic application.

Self-Assembly of Metal-Organic Frameworks into Monolithic Materials with Highly Controlled Trimodal Pore Structures.

We present a two-step template-free approach toward monolithic materials with controlled trimodal porous structures with macro-, meso-, and micropores. Our method relies on two ordering processes in discrete length scales: 1) Spontaneous formation of macroporous structures in monolithic materials by the sol-gel process through the short-range ordered self-assembly of metal-organic frameworks (MOFs), and 2) reorganization of the framework structures in a mediator solution. The Zr-terephthalate-based MOF (UiO-66-NH2 ) was adopted as a proof of concept. The self-assembly-induced phase separation process offered interconnected macropores with diameters ranging from 0.9 to 1.8 μm. The subsequent reorganization process converted the microporous structure from low crystalline framework to crystalline UiO-66. The resultant mesopore size within the skeletons was controlled in the range from 9 to 21 nm. This approach provides a novel way of designing spaces from nano- to micrometer scale in network-forming materials.

Coordination Polymer to Atomically Thin, Holey, Metal-Oxide Nanosheets for Tuning Band Alignment.

Holey 2D metal oxides have shown great promise as functional materials for energy storage and catalysts. Despite impressive performance, their processing is challenged by the requirement of templates plus capping agents or high temperatures; these materials also exhibit excessive thicknesses and low yields. The present work reports a metal-based coordination polymer (MCP) strategy to synthesize polycrystalline, holey, metal oxide (MO) nanosheets with thicknesses as low as two-unit cells. The process involves rapid exfoliation of bulk-layered, MCPs (Ce-, Ti-, Zr-based) into atomically thin MCPs at room temperature, followed by transformation into holey 2D MOs upon the removal of organic linkers in aqueous solution. Further, this work represents an extra step for decorating the holey nanosheets using precursors of transition metals to engineer their band alignments, establishing a route to optimize their photocatalysis. The work introduces a simple, high-yield, room-temperature, and template-free approach to synthesize ultrathin holey nanosheets with high-level functionalities.

Template-free synthesis of biomass-derived hierarchically mesoporous carbon with ultra-small FeNi nanoparticles for oxygen evolution reaction

Highly active and stable catalysts towards electrochemical oxygen evolution reaction are crucial for efficient water splitting and sustainable hydrogen generation. Here we report a carbon supported FeNi catalyst synthesized from an in situ freeze-drying method (fd-FeNi/C) with a commonly seen biomass, jasminum mesnyi flower. The fd-FeNi/C exhibits a N-doped hierarchically mesoporous carbon structure decorated with small FeNi nanoparticles with a small diameter of ∼ 4 nm. Electrochemical measurements show excellent catalytic performance in 1 M KOH solution with an overpotential of 301 mV at the current density of 10 mA cm−2. The value is 41 mV lower than that of the commercial IrO2/C. A small Tafel slope (64.5 mV dec−1) and high stability are also recorded. This work provides a facile, scalable, and template-free approach to convert biomass into highly active electrochemical catalysts, which shows great potential for future applications.

Cobalt sulfides nanoparticles encapsulated in N, S co-doped carbon substrate for highly efficient oxygen reduction

A facile and eco-friendly synthetic method of oxygen reduction reaction (ORR) electrocatalysts is one of crucial steps in the development of large-scale and commercial regenerative energy devices. Herein, a simple and template-free approach is proposed to design CoSx (Co1-xS and Co9S8) nanoparticles encapsulated in N, S-doped carbon substrate (CoSx/NSCS). Interestingly, the carbon substrates are consisted of carbon nanotubes and carbon nanosheets. Moreover, the high-temperature sulfidation step is adopted to form cobalt sulfides and sulfur doping into carbon simultaneously. Benefiting from the N, S doped carbon bedframe and the synergistic effect between cobalt sulfide species and carbon substrate, the optimal CoSx/NSCS-800 (obtained at sulfidation temperature of 800 °C) exhibits robust and excellent ORR electrocatalytic activity in terms of half-wave potential of 0.85 V in alkaline electrolyte. Most importantly, this work, offers great potential to prepare transition metal sulfides nanoparticles integrated with N, S-doped carbon-based electrocatalysts toward ORR.

A template-free method for the synthesis of porous alumina with superhigh specific surface area and large pore volume

Abstract This work demonstrates a facile organic-free and template-free approach for synthesizing spindle-like alumina with large pore volume and high specific surface area via a gas-liquid interfacial method followed by calcination. The influences of different calcination temperatures on the porous alumina were systematically studied. The possible formation mechanism of the spindle-like structures was also investigated. The results exhibited that the as-obtained amorphous alumina calcined at 300 °C had superhigh surface areas (up to 853 m2/g). Furthermore, the adsorption performance of the as-prepared amorphous alumina with high surface area was also evaluated. This spindle-like amorphous alumina showed an excellent adsorption capacity (3284 mg/g) for the removal of Congo red from aqueous solution, which indicate this porous alumina may have great potential applications in adsorption and other related areas.

Rapid and template-free synthesis of copper(I) oxide-graphitic carbon nitride heterojunction for photocatalytic degradation of orange II dye in water

Herein, we report the synthesis of a p-n heterojunction catalyst comprising Cu2O and g-C3N4 via a novel rapid, template-free and facile one-pot approach. The pristine semiconductors and their composite were characterised by X-ray diffraction (XRD), N2 adsorption-desorption isotherms (BET), UV–vis diffuse reflectance spectroscopy, transmission electron microscopy (TEM), field emission scanning electronic microscopy (FESEM) and energy dispersive X-ray spectrometry (EDX). From the Mott-schottky plot, the flat-band potential and carrier density were estimated. Band gap energies of 2.03 and 2.65 eV were calculated for Cu2O and g-C3N4 respectively, which indicate that both catalysts possess excellent optical absorption in the visible region of the solar spectrum. The p-n heterojunction produced a type-II band alignment which promotes the efficient separation of photogenerated electron-hole pairs. The photocatalytic property of the material was evaluated by employing it for the degradation of orange II dye in water. Different mass ratios of Cu2O-g-C3N4 such as 1:1, 3:2, 7:3 and 9:1 were employed in the degradation process. However, Cu2O-g-C3N4 with mass ratio 9:1 displayed the best photocatalytic performance, giving a removal efficiency that is 3.6 times higher than the pristine Cu2O. The decolourisation and mineralisation efficiencies were 85% and 60% after 4 h of treatment. Scavenger studies further revealed the photogenerated holes as the main oxidant species in the photocatalytic reaction.

Surface engineering of hollow carbon nitride microspheres for efficient photoredox catalysis

Photocatalysis has attracted extensive interests because of the potential applications in remedying emerging contaminants and easing ever-increasing energy crisis. Towards practical applications of photocatalysis, exploring competing semiconductor materials is a critical challenge. Herein, hollow carbon nitride microspheres (HCNMS) were synthesized via a template-free hydrothermal approach, in which OH groups (OH-HCNMS) were used for further tuning the surface features. Their properties were thoroughly investigated by a number of advanced characterization methods. The as-prepared HCNMS achieved an impressive p-hydroxybenzoic acid (HBA) degradation rate of 0.013 min−1, which was 4.3 times higher than pristine carbon nitride (C3N4), even higher than some heterostructured or noble metal modified C3N4. The enhanced photooxidation activity of HCNMS was achieved because of the optimized band structure and the deepened valence band edge, as unveiled by both experimental and density functional theory (DFT) calculation results. In addition, OH-HCNMS exhibited an apparent quantum efficiency (AQE) of 3.7% at 420 nm. The improved hydrogen efficiency of OH-HCNMS was ascribed to the surface functionalized OH groups, which react with holes, and release more electrons to participate the water splitting, as well as the modified orbital configuration which facilitates the faster charge carrier transfer.

Efficient immobilization of phospholipase D on novel polymer supports with hierarchical pore structures

In this article, novel epoxy resin-based hierarchical porous polymers (HPSs) have been prepared through a non-sol-gel and template-free approach using crystalline trimethylolpropane (TMP) as porogen. The polymers exhibit dimensional stability and possess 3-dimentional interconnected multi-scale pores. In range of 50 μm~10 nm are ultra-macro-pore in between skeleton, macro-pore on skeleton and meso-pore in network, respectively. The porosity and specific surface area can be adjusted in range of 91.2–82.5% and 225–156 m2/g, respectively. Using three kinds of hierarchical porous polymers as supports phospholipase D (PLD) was effectively immobilized through physical adsorption. Owing to high porosity of the support and improvement of mass transfer the loading amount of PLD reached as high as 223 mg/gsupport and the corresponding specific activity achieved up to 3.75 × 103 U/gsupport. Under optimized conditions and the phosphatidylserine (PS) yield reached 95.5% within 40 min at 45 °C. The immobilized PLD exhibited not only better storage stability and but also resistance to pH and thermal inactivation than free PLD. It was found that 73.5% of PS yield retained after 12 cycling reuses.

Non-aqueous preparation of anatase TiO2 hollow microspheres for efficient dye-sensitized solar cells

TiO2 hollow spheres are fabricated by a facile and template-free approach, which is efficient, cost-saving and favorable for large scale production. The as-prepared TiO2 hollow spheres with diameters ranging from 1 to 1.5 μm and a shell thickness of 150 nm are formed by the self-assembly of nanoparticles with a size of about 12 nm. The mesoporous TiO2 hollow spheres possess a high specific surface area up to 166.2 m2 g−1. TiO2 hollow spheres show superior light trapping characteristics and significantly improve the light scattering ability. The formation of hollow structure is interpreted by the Ostwald ripening mechanism. By employing a double-layered photoanode made of the as-prepared TiO2 hollow spheres as the overlayer and P25 as the bottom layer, the dye-sensitized solar cell achieved a power conversion efficiency of 7.90%, which is ascribed to the enhanced dye loading and light scattering ability of TiO2 hollow spheres.

Synergistically effective and highly visible light responsive SnO2-g-C3N4 nanostructures for improved photocatalytic and photoelectrochemical performance

This paper reports the facile and scalable fabrication of mesoporous and high surface area tin oxide and tin oxide-graphitic carbon nitride nanostructures {SnO2, SnO2-C3N4 (2 mM) and SnO2-g-C3N4 (4 mM)} using a template-free hydrothermal approach. The overall characterisation revealed a high surface area (~181 m2g−1) with a mesoporous nature, relatively small particle size of SnO2 (~2–3 nm) grown successfully on g-C3N4 sheets, and significantly improved optical behaviour for visible light utilisation. Comparative screening of different SnO2-based nanostructures revealed significant improvements in visible-light induced photocatalytic degradation and photoelectrochemical performance. The visible light-induced degradation of model pollutants, such as Methylene blue (MB) and Congo red (CR), was achieved using SnO2-g-C3N4 (4 mM) with total efficiencies of ~99.38% and ~96%, respectively. The optimal SnO2-g-C3N4 (4 mM) as a photocatalyst showed first order rate constants for MB and CR degradation of 6.39 × 10−2 min−1 and 2.9 × 10−2 min−1, respectively. Moreover, the investigation of different modified photoelectrodes of SnO2-g-C3N4 (4 mM) and SnO2-g-C3N4 (2 mM) show more than eight and five times higher photoelectrochemical performance than that of SnO2, respectively. The possible synergistic effect makes the SnO2-g-C3N4 (4 mM) nanostructure an exceptional photocatalytic and photoresponsive material under visible light that can be used for future environmental and energy-related purposes.

Phosphorous doped carbon nitride nanobelts for photodegradation of emerging contaminants and hydrogen evolution

Photocatalysis has demonstrated great potentials for both environmental remediation and green energy production. In this study, a simple solvothermal template-free approach was employed for the first time to synthesize phosphorous doped carbon nitride nanobelt (PCNNB). Advanced characterizations, for instance, 13C NMR, 31P NMR, and XPS results indicated that P was substitutionally doped at the corner-carbon of the carbon nitride frameworks. The introduction of P dopants inhibited the polymerization between NH2 groups within PCNNB, enabling the decrease in nanobelt width for the exposure of more active sites. Therefore, the optimized P-CN-NB-2 (derived from 0.2 mM H3PO4) rendered enhanced p-hydroxybenzoic acid (HBA) degradation nearly 66-fold higher than bulk g-C3N4, among the most efficient g-C3N4-based photocatalysts as reported. In addition, the P-CN-NB-1 (derived from 0.02 mM H3PO4) exhibited about 2 times higher H2 evolution rate than CNNB. Density functional theory (DFT) calculations were also conducted to provide insights into the mechanism.