Clay Template Research Articles

Morphologically tunable nanoarchitectonics of mixed kaolin-halloysite derived nitrogen-doped activated nanoporous carbons for supercapacitor and CO2 capture applications

We report an integrated approach by combining in-situ activation, doping and natural nanotemplating to design low-cost and highly efficient N-doped nanoporous carbons for energy storage and carbon capture applications. N-doped nanoporous carbons are prepared by impregnating sucrose, 3-amino 1,2,4-triazole and the ZnCl2 into the nanochannels of the mixed kaolin-halloysite nanotube nanoclay, followed by carbonization and clay template removal. The prepared materials exhibit micro and mesoporosity, high specific surface areas (1360–1695 m2 g−1), and nitrogen content (7.73–12.34 wt%). The optimized material offers the specific capacitance of 299 F g−1 (0.3 A g−1) and 134 F g-1 (10 A g−1) with excellent cycling stability (91% capacity retention after 4000 cycles/5 A g−1). N-doping together with the interconnected micro and mesoporous structure, offers a more ion accessible surface and further provides enhanced charge transfer, hydrophilicity, and the interaction of the electrode-electrolyte ions. The optimized material adsorbs 24.4 mmol g−1 of CO2 at 30 bar pressure and 0 °C. The synthesized materials performed better as supercapacitor and CO2 adsorbent than halloysite clay, kaolin clay, activated carbon, nanoporous carbons, and mesoporous silica. The method presented here will provide a unique platform for synthesizing a series of advanced nanostructures for electrochemical and carbon capture applications.

Greenalite Nanoparticles in Alkaline Vent Plumes as Templates for the Origin of Life.

Mineral templates are thought to have played keys roles in the emergence of life. Drawing on recent findings from 3.45–2.45 billion-year-old iron-rich hydrothermal sedimentary rocks, we hypothesize that greenalite (Fe3Si2O5(OH)4) was a readily available mineral in hydrothermal environments, where it may have acted as a template and catalyst in polymerization, vesicle formation and encapsulation, and protocell replication. We argue that venting of dissolved Fe2+ and SiO2(aq) into the anoxic Hadean ocean favored the precipitation of nanometer-sized particles of greenalite in hydrothermal plumes, producing a continuous flow of free-floating clay templates that traversed the ocean. The mixing of acidic, metal-bearing hydrothermal plumes from volcanic ridge systems with more alkaline, organic-bearing plumes generated by serpentinization of ultramafic rocks brought together essential building blocks for life in solutions conducive to greenalite precipitation. We suggest that the extreme disorder in the greenalite crystal lattice, producing structural modulations resembling parallel corrugations (∼22 Å wide) on particle edges, promoted the assembly and alignment of linear RNA-type molecules (∼20 Å diameter). In alkaline solutions, greenalite nanoparticles could have accelerated the growth of membrane vesicles, while their encapsulation allowed RNA-type molecules to continue to form on the mineral templates, potentially enhancing the growth and division of primitive cell membranes. Once self-replicating RNA evolved, the mineral template became redundant, and protocells were free to replicate and roam the ocean realm.

Utilizing exfoliated clay–poly(norbornene) nanocomposite prepared by metal-mediated surface-initiated polymerization as model end-tethered polymers on an organoclay substrate

Current interest in dispersion strategies for nanoparticle fillers is driving research into covalently attached polymer brushes. The primary need for these “hairy nanoparticles” is for testing and developing new technologies based on polymer nanocomposites. To that end, we have prepared polymer nanocomposites with covalently tethered chains on a naturally occurring montmorillonite clay template via a metal-mediated surface-initiated ring opening metathesis polymerization approach. The nanocomposites were characterized in terms of polymer:clay composition and of various chain architecture parameters such as molecular weight, polydispersity index, and grafting density.

Preparation and Characterization of Clay-polymer Nanocomposite Having Covalently-bound poly(norbornenes) with Pendant Cholesterols

We have successfully prepared a clay-based polymer nanocomposite having grown cholesterol bearing poly(norbornene) brushes end-tethered from a naturally-occurring montmorillonite clay template. The synthesis of this hybrid material involved the treatment of the clay with first generation Grubbs catalyst, a ruthenium alkylidene, which induced a ring-opening metathesis and subsequent surface initiated polymerization of the cholesterol bearing monomer. This results in an inorganic/organic hybrid functional nanomaterial where the inclusion of the clay particles in a liquid crystalline domain modifies the thermal transitions.

Synthesising chain-like, interconnected Pt nanoparticles using a tubular halloysite clay template for an efficient counter electrode in dye-sensitised solar cells

We report an inexpensive fabrication route of a mesoporous counter electrode made of chain-like Pt nanoparticles using a tubular halloysite clay template.

Synthesis of Highly Reactive Subnano-Sized Zero-Valent Iron Using Smectite Clay Templates

A novel method was developed for synthesizing subnano-sized zero-valent iron (ZVI) using smectite clay layers as templates. Exchangeable Fe(III) cations compensating the structural negative charges of smectites were reduced with NaBH(4), resulting in the formation of ZVI. The unique structure of smectite clay, in which isolated exchangeable Fe(III) cations reside near the sites of structural negative charges, inhibited the agglomeration of ZVI resulting in the formation of subnanoscale ZVI particles in the smectite interlayer regions. X-ray diffraction revealed an interlayer spacing of approximately 5 A. The non-structural iron content of this clay yields a calculated ratio of two atoms of ZVI per three cation exchange sites, in full agreement with the X-ray diffraction (XRD) results since the diameter of elemental Fe is 2.5 A. The clay-templated ZVI showed superior reactivity and efficiency compared to other previously reported forms of ZVI as indicated by the reduction of nitrobenzene; structural Fe within the aluminosilicate layers was nonreactive. At a 1:3 molar ratio of nitrobenzene/non-structural Fe, a reaction efficiency of 83% was achieved, and over 80% of the nitrobenzene was reduced within one minute. These results confirm that non-structural Fe from Fe(III)-smectite was reduced predominantly to ZVI which was responsible for the reduction of nitrobenzene to aniline. This new form of subnanoscale ZVI may find utility in the development of remediation technologies for persistent environmental contaminants, for example, as components of constructed reactive domains such as reactive caps for contaminated sediments.

Optical Non‐Linearity from Montmorillonite Intercalated with a Chromophore‐Containing Dendritic Structure: A Self‐Assembly Approach

AbstractChromophore‐containing dendritic structures (G1, G2) are utilized to intercalate layered silicates, which results in a large d‐spacing up to 126 Å. An exfoliated morphology is obtained by mixing the dendritic structure intercalated layered silicates with polyimide in N,N‐dimethylacetamide solution. The dendritic structures attached on the clay template would arrange in a non‐centrosymmetric manner. This self‐assembled arrangement brought about the electro‐optical coefficients of 5–6 pm · V−1 for these relatively low chromophore‐containing organic/inorganic nanocomposites without resorting to poling. Excellent temporal stability (100 °C) is also achieved.magnified image

Ubiquitous Burgess Shale–style “clay templates” in low-grade metamorphic mudrocks

Despite the Burgess Shale’s (British Columbia, Canada) paleobiological importance, there is little consensus regarding its taphonomy. Its organic fossils are preserved as compressions associated with phyllosilicate fi lms (“clay templates”). Debate focuses on whether these templates were fundamental in exceptional preservation or if they formed in metamorphism, meaning that it is important to establish the timing of their formation relative to decay. An early diagenetic origin has been proposed based on anatomy-specifi c variations in their composition, purportedly refl ecting contrasts in decay. However, we demonstrate that these films bear a remarkable similarity to those that occur on organic fossils in graptolitic mudrocks and form as a normal product of low-grade metamorphism. Such phyllosilicates may also occur within voids created by volume loss in maturation, a process that may have aided their formation. In bedding-plane assemblages from graptolitic mudrocks, different taxa are associated with distinct phyllosilicates. This likely refl ects stepwise maturation of their constituent kerogens in an evolving hydrothermal fl uid, with different hyllosilicates forming as each taxon progressively underwent maturation. These observations provide an analogue for the distribution and composition of phyllosilicates on Burgess Shale fossils, which we interpret as refl ecting variations in the maturation of their constituent tissues. Thus, their clay templates seem unremarkable, forming too late to account for exceptional preservation.

The Template Polymerization of 12-Methacryloyloxydodecanoate Ions in LDH Clay

Abstract The LDH clay template polymerization of 12-methacryloyloxydodecanoate (MADA) ions under UV light irradiation resulted in the formation of preferential meso polymer ions through radical propagation in a parallel-oriented MADA hybrid assembly.

Aqueous and Gaseous Adsorption from Montmorillonite−Carbon Composites and from Derived Carbons

Clay-carbon composites and the carbons derived from demineralization of the clay template were examined for their aqueous adsorption properties (2,4,6-trichlorophenol and methylene blue) and for their gas adsorption/separation abilities regarding CO(2), CH(4), and N(2) gases. The sorption results are discussed in relation with their structural properties (surface area, pore width and volume, and surface chemistry). It was found that the properties of the adsorbents depend highly on the synthetic route, for instance, on the use of clay or H(2)SO(4) as structure mediating and activating agents, respectively. Particularly, the simultaneous use of clay and H(2)SO(4) leads to a synergistic action, which imparts to the final solids the highest sorption capacity and the best potential for separation of CO(2) from gaseous mixtures of CH(4) and N(2).

Small angle neutron scattering studies and kinetic analysis of laponite–enzyme hydrogels in view of biosensors construction

Clay hydrogels were designed as an immobilization matrix for electroactive enzymes at the surface of electrodes. Such materials are prepared by drying an aqueous colloidal suspension of laponite clay and enzyme on the surface of the electrodes. The properties of such materials have been investigated with regards to their structure and permeability, which determine the entrapment efficiency and the accessibility of the analyses to the enzymatic sites. The structure of such materials containing similar amounts of globular protein (bovine serum albumin (BSA)) and laponite have been investigated both in the dry and swollen states by means of small angle neutron scattering (SANS). The macroscopic orientation parallel to the faces of the dry films and the short-range ordering in the direction perpendicular to the faces was observed. This structure corresponds to that of the clay template swollen by the proteins. These structural features resist against moderate swelling by a concentrated electrolytic solution. The macroscopic orientation and the short-range order progressively disappear upon swelling with aqueous solutions of decreasing ionic strength. Since the structure turns from a quasi-impermeable stack of clay sheets to an open isotropic structure with enhanced accessibility below 100 mM of phosphate buffer, the sensitivity of an enzymatic clay-modified electrode (CME) working with the polyphenol oxidase (PPO) increases when the ionic strength of the swelling medium decreases. However, the gain of sensitivity remains moderate although the structural changes are huge. The rate determining mechanism seems to be a diffusion of the reacting species through defects (microchannels) inside the film as was previously proposed based on electrochemical and kinetics studies on the electrodes.

Templated Synthesis of Carbon Materials from Zeolites (Y, Beta, and ZSM-5) and a Montmorillonite Clay (K10): Physical and Electrochemical Characterization

New high surface area carbon materials were prepared at low temperature (600 °C) using zeolite (Y, Beta, and ZSM-5) and montmorillonite clay (K10) templates. Acrylonitrile, furfuryl alcohol, pyrene, and vinyl acetate precursors were polymerized and carbonized in each of the inorganic matrixes without the addition of a polymerizing agent. The templates were removed by acid demineralization and the resulting carbon materials were physically characterized by infrared spectroscopy, BET (N2) surface area analysis, energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), and elemental analyses. Electrochemical characterizations were also conducted. Cyclic voltammetry was employed to examine the synthesized carbons in the oxidation of catechol to hydroquinone and quinone, a model reaction that is known to be surface dependent. The identities of both the template and the substrate affected the electrochemical response. Additionally, the ability of the new carbons to intercalate and deintercalate ...

Clay/Carbon Nanocomposites as Precursors of Electrode Materials for Lithium-Ion Batteries and Supercapacitors

Chars prepared by pyrolysis of organic precursors (Indoine Blue, Safranine, Pyrene) in the interlayer space of taeniolite were used as electrode materials in lithium/carbon cells. Due to oxidation of interlayer carbon by the silicate host, they contain a high amount of surface groups, and their essentially mesoporous character is attributed to the space liberated by the elimination of the clay template. A large reversible capacity for lithium insertion, up to 900 mAh/g, was detected for these materials. The chars presented a high capacitance which could reach 85 F/g in KOH electrolyte if they were formed below 850°C. Such a high value relatively to the low BET surface area of the chars is strictly related to the important mesopore volume and to the rich surface functionality.

Designer Carbons Templated by Pillared Clays: Lithium Secondary Battery Anodes

AbstractThis work describes the designed synthesis and physical characterization of carbons containing predictable microporosity. The approach is to pyrolyze aromatic hydrocarbons such as pyrene within a pillared clay. The pillared clay serves two functions. It performs as the inorganic template around which the designer carbon can be formed, and it acts as an acid catalyst to promote condensation of the aromatics similar to the Schöll reaction. These precursors then undergo thermal polymerization and carbonization at 700 °C. Removal of the pillared clay template is accomplished by standard acid demineralization techniques, leaving behind carbons with 15 to 50 Å holes.

The Polymerization of Heterocycles on Clay Templates

ABSTRACTThe oxidizing power of clays is put to use for the polymerization of heterocycles (pyrrole- and thiophene- types) in the 2D-interfoliar space and on the external surface of the clay particles. A mechanism is proposed for the oxidative polymerization.