Nanocrystalline Domains Research Articles

Synthesis, characterization and analytical application of polyaniline tin(IV) molybdophosphate composite with nanocrystalline domains

Polyaniline–tin(IV)molybdophosphate nanocomposite has been synthesized by incorporating polyaniline into inorganic exchanger tin(IV)molybdophosphate. Simultaneous TGA–DTA, FTIR, XRD, HRTEM and EDS have been used to characterize this composite material. The polyaniline–tin(IV)molybdophosphate (PATMP) behaves as bifunctional and strong acid cation exchanger with IEC of 1.79meqg−1 for Na+ ions. Thermal analysis of the material shows that the material retains 75% of its ion-exchange capacity up to 600°C. Adsorption behavior of metal ions in different solvents with varying concentration has also been explored. The sorption studies revealed that the material is selective for Pb(II) and Cu(II) ions. The analytical utility of the material has been explored by achieving some binary separations of metal ions on its column based on the distribution coefficients. Pb(II) and Cu(II) have been selectively removed from synthetic mixtures of Pb(II)–Mn(II), Pb(II)–Ni(II), Cu(II)–Mn(II) and Cu(II)–Ni(II).

Mesoporous Zirconium Phenylenesiliconate-phosphonate Hybrids with Ordered Lamellar Nanostructures.

Novel ordered lamellar mesostructure pZrPS-2 was hydrothermally prepared by using zirconium propoxide and 4-(EtO)2OPC6H4Si(OEt)3 (pPPS-E), which was hydrolyzed to organic building units substituted with both siliconate and phosphonate groups, in the presence of Cn TAB and TMAOH. The pZrPS-2 materials were obtained at a Zr/PPS ratio of 2 or higher and the basal spacing was increased by using a longer-chain surfactant (n = 12-18). Removal of the occluded surfactants at 300 °C resulted in retention of the lamellar structure with negligible shrinkage of the interlayer distance. Nitrogen adsorption studies revealed the ordered mesoporous nature of pZrPS-2 with a pore diameter of approximately 2 to 3 nm. The lamellar structure is assumed to be composed of layers that include zirconia-based crystalline nanodomains and interlayer pillars mainly based on PPS units. Although lamellar structures with the same crystalline phase also formed when no surfactant was added or when the meta isomer of PPS was used, no mesoporous materials were obtained except pZrPS-2. A possible schematic model to elucidate these results is also proposed.

Role of nanocrystalline domain size on the electrochemical double-layer capacitance of high edge density carbon nanostructures

AbstractNanostructured carbon materials, especially activated carbon, carbon nanotubes, and graphene, have been widely studied for supercapacitor applications. To maximize the efficacy of these materials for electrochemical energy storage, a detailed understanding of the relationship between the nanostructure of these materials and their performance as supercapacitors is required. A fundamental structural parameter obtained from the Raman spectra of these materials, the in-plane correlation length or nanocrystalline domain size, is found to correlate with the electrochemical capacitance, regardless of other morphological features. This correlation for a common nanostructural characteristic is believed to be the first result of its kind to span several distinct nanostructured carbon morphologies, including graphene–carbon nanotubes hybrid materials, and may allow more effective nanoscale engineering of supercapacitor electrode materials.

21.4: Deposition Conditions and HRTEM Characterization of CAAC IGZO

Crystallinity and texture of c‐axis aligned crystal indium gallium zinc oxide (CAAC IGZO) films deposited by RF reactive sputtering were studied and characterized over a range of deposition conditions. The characteristic CAAC (009) peak at 2θ=30° was observed by X‐ray diffraction, and nanocrystalline domain texture was determined using a general area detector diffraction system (GADDS). Highly ordered CAAC films were obtained near the InGaZnO4 composition at a substrate temperature of 310°C and in 10% O2. High‐resolution transmission electron microscopy (HRTEM) confirmed the formation of CAAC showing 2‐3 nm domains aligned over 15 nm x 15 nm fields of view. Cross‐section HRTEM of the CAAC/substrate interface shows formation of an initially disordered IGZO layer prior to CAAC formation, suggesting a nucleation mechanism similar to ZnO thin films.

Conjugated foldamers with unusually high space-charge-limited current hole mobilities.

Charge carrier mobility and its optimization play a critical role in the development of cutting-edge organic electronic and optoelectronic devices. Even though space-charge-limited current (SCLC) hole mobilities as high as 1.4 cm(2) V(-1) s(-1) have been reported for microscopically sized highly ordered liquid-crystalline conjugated small molecules, the SCLC hole mobility of device-sized thin films of conjugated polymers is still much lower, ranging from 10(-6) to 10(-3) cm(2) V(-1) s(-1). Herein, we report the synthesis, characterizations, and thin-film SCLC mobility of three discotic conjugated polymers, INDT-TT, INDT-BT, and INDT-NDT. Optical studies indicate that polymer INDT-NDT adopts a folded conformation in solutions of good or poor solvents, whereas polymer INDT-TT stays as random monomeric chains in good solvents and interchain aggregates in poor solvents. INDT-BT polymer chains, however, stay as foldamers in dilute solutions of good solvents but interchain aggregates in concentrated solutions or poor solvents. Circular dichroism spectroscopy provides clear evidence for the helical folding of INDT-NDT in solutions. Thin films spin-coated from 1,2-dichlorobenzene solutions of the polymers show SCLC hole mobility of 2.20 × 10(-6), 8.79 × 10(-5), and 2.77 × 10(-2) cm(2) V(-1) s(-1) for INDT-TT, INDT-BT, and INDT-NDT, respectively. HRTEM and powder XRD measurements show that INDT-NDT pristine thin films contain nanocrystalline domains, whereas the INDT-TT and INDT-BT films are amorphous. Thin films of INDT-NDT:PC71BM blends show increased crystallinity and further improved SCLC hole mobility up to 1.29 × 10(-1) cm(2) V(-1) s(-1), one of the highest SCLC mobility values ever recorded on solution-processed organic semiconducting thin films. The persistent folding conformation of INDT-NDT is believed to be responsible for the high crystallinity of its thin films and its high SCLC mobilities.

Dislocation Effects on the Diffraction Line Profiles from Nanocrystalline Domains

A Pd nano-polycrystalline microstructure was simulated by molecular dynamics, including edge or screw dislocations in one of the 50 grains, so as to produce a realistic model of nanocrystalline domain with line defect. The same crystalline domain was also studied, with or without line defects, as a free-standing, isolated nanocrystal. Atomic coordinates of the selected domain were used to generate powder patterns by means of the Debye scattering equation, and these patterns were used as “experimental” data to test existing methods of line profile analysis in controlled condition, i.e., with known type and density of defects. Results show that the Krivolgaz–Wilkens theory of dislocation line broadening qualitatively agrees with the MD model, but errors can be larger than 50 pct. A critical issue arises from the instability of the Krivolgaz–Wilkens model when all line profile parameters are simultaneously refined: reasonable results can be obtained by fixing or restricting some parameters.

Toward a reference material for line profile analysis

A powder obtained by ball milling a commercial FeMo alloy has been identified and investigated as possible reference material for powder diffraction line profile analysis. Ball milling yields micrometer-scale agglomerate particles made of rounded nanocrystalline domains with extensive lattice defects, so as to produce both size and strain contributions to the line profiles. The capability of a modern whole-powder pattern modeling to accurately quantify those aspects and the stability of the powder over a decade are shown and discussed.

Charge trapping in mixed organic donor-acceptor semiconductor thin films.

A pump-probe method, whereby trapped charges are optically induced to contribute to the total photocurrent, is applied to quantitatively determine the trap density in small-molecule organic semiconductor thin films and donor-acceptor blends used in organic solar cells. The trapped charge density is correlated to the cell performance, and the dependence of charge trapping on the presence of nanocrystalline domains is discussed.

Phonon confinement model applied on the Raman spectra of CVD diamond films grown through graphite etching

Diamond films, in micro and nanocrystalline (MCD ad/or NCD) domain, were grown on silicon substrate from graphite etching as a carbon source with atomic hydrogen, instead of using conventional hydrocarbon in the feed gas. A Graphite plate was used as sample support in a hot filament chemical vapour deposition. Scanning electron microscopy (SEM) images were used to analyze the nucleation rate of diamond films. The films grown during 15 min at 600 and 700 oC presented the higher nucleation rate with grain size in a submicrometer dimension. The high density of NCD formation in the first stage of film growth is attributed to the high amount of available carbon, even from this process governed by the graphite hydrogen etching. Micro-Raman spectroscopy demonstrated the feature of NCD coating, particularly the peak at 1150 cm-1 is attributed to trans-polyacetilene (t-Pa). Also, this high amount of NCD population in such diamond films induces a broadening and shape changes in Raman peak at 1332 cm-1. This behaviour was studied from phonon confinement model and the NCD crystallite size was evaluated in the range of 18.5 up to 14.3 nm as the in-plane correlation length La

Mechanochemically Synthesized Nanocrystalline Sb2S3Particles

Nanocrystalline Sb2S3 particles have been synthesized from Sb and S powders by high-energy milling in a planetary mill using argon protective atmosphere. X-ray di raction, particle size analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, electron di raction, high resolution transmission electron microscopy, UV-VIS, and di erential scanning calorimetry methods for characterization of the prepared particles were applied. The powder X-ray di raction pattern shows that Sb2S3 nanocrystals belong to the orthorhombic phase with calculated crystallite size of about 36 nm. The nanocrystalline Sb2S3 particles are constituted by randomly distributed crystalline nanodomains (20 nm) and then these particles are forming aggregates. The monomodal distribution of Sb2S3 particles with the average hydrodynamic parameter 210 nm was obtained. The quanti cation of energy dispersive X-ray spectroscopy analysis peaks give an atomic ratio of 2:3 for Sb:S. The optical band gap determined from the absorption spectrum is 4.9 eV, indicating a considerable blue shift relative to the bulk Sb2S3. Di erential scanning calorimetry curves exhibit a broad exothermic peak between 200 and 300 ◦C, suggesting recovery processes. This interpretation is supported by X-ray di raction measurements that indicate a 23-fold increase of the crystallite size to about 827 nm as a consequence of application of high temperature process. The controlled mechanochemical synthesis of Sb2S3 nanoparticles at ambient temperature and atmospheric pressure remains a great challenge.

Multinuclear Solid-State NMR Studies of Polymer-Supported Scandium Triflate Catalysts

Scandium(III) trifluoromethanesulfonate [Sc(OTf)3] is extensively used in organic synthesis to catalyze a wide variety of carbon–carbon bond-forming reactions in aqueous media. It has previously been demonstrated that it is possible to immobilize Sc(OTf)3 in polystyrene (PS) to form the heterogeneous catalysts, microencapsulated (ME) Sc(OTf)3. The ME catalysts are recoverable, reusable, often reduce metal leaching, and have activity similar to that of their homogeneous counterparts. Aside from preliminary scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) imaging studies and solution 45Sc NMR studies, there is little information available about the molecular and bulk structure of the ME catalyst. In this regard, we have conducted a 45Sc solid-state NMR investigation of the Sc environments in the crystalline and ME forms of anhydrous Sc(OTf)3 and hydrated Sc(OTf)3·8H2O. Additional solid-state 1H, 19F, and 13C NMR and powder X-ray diffraction experiments provide information that is complementary to that obtained from the 45Sc NMR spectra, allowing for structural models of ME complexes to be proposed. The principal findings are that Sc(OTf)3 is hydrated upon microencapsulation to form Sc(OTf)3·8H2O. 1H–45Sc TRAPDOR and 1H–19F CP SSNMR experiments and powder X-ray diffraction experiments suggest that Sc is dispersed throughout the polymer within nanocrystalline domains of Sc(OTf)3·8H2O. The approach outlined here should be applicable for the characterization of many other polymer-supported metal-based catalysts.

Structural analysis of lignin-derived carbon composite anodes

The development of novel lignin-based carbon composite anodes consisting of nanocrystalline and amorphous domains motivates the understanding of the relationship of the structural properties characterizing these materials, such as crystallite size, intracrystallitedspacing, crystalline volume fraction and composite density, with their pair distribution functions (PDFs), obtained from both molecular dynamics simulation and neutron scattering. A model for these composite materials is developed as a function of experimentally measurable parameters and realized in 15 composite systems, three of which directly match all parameters of their experimental counterparts. The accurate reproduction of the experimental PDFs using the model systems validates the model. The decomposition of the simulated PDFs provides an understanding of each feature in the PDF and allows for the development of a mapping between the defining characteristics of the PDF and the material properties of interest.

A correlation between the magnetic and structural properties of isochronally annealed Cu-free FINEMET alloy with composition Fe72B19.2Si4.8Nb4

In this paper, structural changes in Cu-free FINEMET alloy (Fe72B19.2Si4.8Nb4) invoked by isochronal thermal annealing were investigated by synchrotron X-ray diffraction (SXRD) and X-ray absorption near-edge spectroscopy techniques. Detailed radial distribution function analysis of SXRD data showed that the first coordination shell in the amorphous matrix is preserved for annealing up to 400 °C (1 h), whereas changes were observed in the second coordination shell. Annealing at 600 °C (1 h) showed crystalline phase emanating over the amorphous background in SXRD data and a corresponding large decrease in the width of the first coordination shell. The width of the second coordination shell decreased with increasing annealing temperature. The magnetic properties such as remanence field, saturation magnetization and loss were found to have a positive correlation with the changes in the structural parameters of the second coordination shell, for all the samples (as quenched as well as annealed at various temperatures). We propose that the rearrangement of magnetic amorphous matrix on annealing also contributes to modifying the exchange interaction between ferromagnetic nanocrystalline domains and hence changes magnetic parameters, in addition to the growth of these domains, on annealing.

Effect of Nanocrystalline Domains in Photovoltaic Devices with Benzodithiophene-Based Donor–Acceptor Copolymers

We have investigated the effects of thin-film morphology on the photovolatic performance for a series of donor–acceptor copolymers based on benzodithiophene donor and benzothiadiazole acceptor units. Photovoltaic devices incorporating polymer:fullerene blends show highest efficiencies (up to 6%) for those polymers exhibiting the least degree of crystallinity in X-ray diffraction patterns and a corresponding lowest surface roughness in thin films. We find that the existence of such crystalline domains in thin polymer films correlates well with spectral signatures of polymer chain aggregates already present in solution prior to casting of the film. Polymer solubility and casting conditions therefore appear to be crucial factors for enhancing efficiencies of photovoltaic devices based on such donor–acceptor copolymers. To examine why the presence of crystallite domains lowers device efficiencies, we measured exciton diffusion lengths by modeling the time-dependent photoluminescence from thin polymer films de...

Green Catalytic Approach for the Synthesis of Functionalized Nanocellulose from Palm Tree Biomass

Oil palm is a major agricultural product in Malaysia and it covers approximately 5 million hectares of land. Palm tree biomass is a by-product of oil palm cultivation. Biomass is a complex structure composed of cellulose, hemicelluloses and lignin. Cellulose, which gives the mechanical properties to the natural fiber, is organized in micro-fibrils enclosed by the other two main components: hemicellulose and lignin. Cellulose microfibrils can be found as intertwined microfibrils in the cell wall (220 μm in diameter and 100 40,000 nm in length). Cellulose microfibrils are in turn exist in cellulose nanofibers having diameter of 550 nm and length several millimeters conformed by nanocrystalline domains and amorphous regions. Nanocellulose, which is a degradation product of cellulose, has recently come to public attention because of its great mechanical properties combined with low molecular weight, renewability and biodegradability. Another advantage of nanofibrillar cellulose is that their production does not interfere with the food chain, therefore, they can be considered as socially sustainable raw materials. However, before the nanocellulose can be fully utilized to fabricate smart and environmentally friendly new high-tech products. Most common applications of nanocellulose are for polymer composite, bioplastics, films, foams, gels, cosmetics, dimensionally stable thickener and emulsion, implant material, biodegradable tissue scaffold, suture, drug delivery vehicle, filter paper, speaker membrane, battery membrane, concrete, drilling muds & enhanced oil recovery, water treatment, etc. Several methods have been proposed for the extraction/preparations of nanocellulose which involve extensive chemical and mechanical treatments which are not environmentally friendly. This paper reviewed various methods along with their limitations for the controlled structure synthesis of functionalized nanocellulose from palm tree biomass. The green catalytic approaches are schematically outlined.

Reversible Assembly of β-Sheet Nanocrystals within Caddisfly Silk

Nuclear magnetic resonance (NMR) and X-ray diffraction (XRD) experiments reveal the structural importance of divalent cation-phosphate complexes in the formation of β-sheet nanocrystals from phosphorylated serine-rich regions within aquatic silk from caddisfly larvae of the species Hesperophyla consimilis. Wide angle XRD data on native caddisfly silk show that the silk contains a significant crystalline component with a repetitive orthorhombic unit cell aligned along the fiber axis with dimensions of 5.9 Å × 23.2 Å × 17.3 Å. These nanocrystalline domains depend on multivalent cations, which can be removed through chelation with ethylenediaminetetraacetic acid (EDTA). A comparison of wide angle X-ray diffraction data before and after EDTA treatment reveals that the integrated peak area of reflections corresponding to the nanocrystalline regions decreases by 15-25% while that of the amorphous background reflections increases by 20%, indicating a partial loss of crystallinity. (31)P solid-state NMR data on native caddisfly silk also show that the phosphorylated serine-rich motifs transform from a rigid environment to one that is highly mobile and water-solvated after treatment with EDTA. The removal of divalent cations through exchange and chelation has therefore caused a collapse of the β-sheet structure. However, NMR results show that the rigid phosphorus environment is mostly recovered after the silk is re-treated with calcium. The (31)P spin-lattice (T1) relaxation times were measured at 7.6 ± 3.1 and 1 ± 0.5 s for this calcium-recovered sample and the native silk sample, respectively. The shorter (31)P T1 relaxation times measured for the native silk sample are attributed to the presence of paramagnetic iron that is stripped away during EDTA chelation treatment and replaced with diamagnetic calcium.

Probing anodic oxidation kinetics and nanoscale heterogeneity within TiO2 films by Conductive Atomic Force Microscopy and combined techniques

Anodic oxidation of titanium in acid electrolytes allows to obtain a thin, compact oxide layer with thickness, structure, color, and electrical properties that vary with process parameters imposed, among which cell voltage has a key effect. Although oxidation kinetics have been investigated in several research works, a broader vision of oxide properties–including thickness and structure–still has to be achieved, especially in the case of very thin oxide films, few tens of nanometers thick. This is vital for engineered applications of nanostructured TiO2 films, as in the field of memristive devices, where a precise control of oxide thickness, composition and structure is required to tune its electrical response. In this work, oxide films were produced on titanium with thickness ranging from few nanometers to 200nm. Oxide thickness was estimated by coulometry and spectrophotometry. These techniques were then combined with C-AFM, which provided a deeper understanding of oxide thickness and uniformity of the metal surface and probed the presence of crystalline nano-domains within the amorphous oxide phase affecting the overall film electrical and optical properties.

Effect of Mixed Layer Crystallinity on the Performance of Mixed Heterojunction Organic Photovoltaic Cells

Organic vapor-phase deposition (OVPD) is used to grow tetraphenyldibenzoperiflanthen (DBP):C70 mixed heterojunction photovoltaic devices. Compared with vacuum thermal evaporation (VTE), the OVPD-grown film develops nanocrystalline domains of C70. Optimized OVPD-grown OPVs have a 61% fill factor for a 100 nm active layer thickness, whereas VTE-grown devices have a 47% fill factor at the same thickness.

Silicon effect on the composition and structure of nanocalcium phosphates: In vitro biocompatibility to human osteoblasts

Nanostructured calcium phosphates, such as nanohydroxyapatite (HAP) and HAP with silicon content (HAP-Si) of 0.47wt.% (1% SiO2), 2.34wt.% (5% SiO2) and 4.67wt.% (10% SiO2) in the final product, were synthesized by aqueous precipitation, freeze dried and then calcined at 650, 950 and 1150°C. The obtained materials were investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrometry, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) imaging. From the analysis of the XRD patterns, the HAP and β-tricalcium phosphate (β-TCP) phases were identified and their amounts in the samples were estimated. The size of HAP and β-TCP crystallites was estimated to be in the nanocrystalline domain. FTIR spectra showed the presence of characteristic vibrations for P–O, H–O and Si–O groups and their modification with Si content and calcination temperature. TEM, SEM and AFM images also revealed the morphology of the particles and of their aggregates. These materials have been used to manufacture scaffolds which were tested for their influence on adhesion and proliferation of cells, in human osteoblast culture, considering their further use in bone reconstruction. It was found that an appropriate addition of silicon in nanocalcium phosphate scaffolds leads to an enhanced adhesion and proliferation of cells in osteoblasts in vitro.

From parallel to single crystallization kinetics in high-density amorphous ice

The isobaric transformation behavior of unannealed (uHDA) and expanded (eHDA) high-density amorphous ice at pressures up to 0.20 GPa is compared using powder x-ray diffraction and dilatometry. eHDA shows high thermal stability and crystallizes to a single ice phase only, whereas uHDA shows much lower thermal stability and always crystallizes to a mixture of ice phases. Unexpectedly, at low temperatures hexagonal ice grows first from uHDA, whereas this phase never crystallizes from eHDA. This leads us to conclude that hidden structural order in the form of nanocrystalline domains is present in uHDA, which triggers growth of hexagonal ice. By contrast, these ordered domains are absent in eHDA, which appears to be a homogeneous material and, thus, could be considered as a candidate for the low-temperature proxy of the proposed high-density liquid phase of water. The present work provides the basis for further experimental studies aiming at investigating this possibility since it establishes that the well-studied uHDA is not the right material to be studied in this context, whereas the more recently discovered eHDA is.