Agglomeration Of Nanocrystals Research Articles

Dual carbon confining SnO2 nanocrystals as high-performance anode for sodium-ion batteries

The increasing global demand for sustainable energy sources has driven research into sodium-ion batteries (SIBs) for large-scale energy storage. However, their electrochemical performance is hindered by poor reaction kinetics and significant volume expansion in electrode materials. In this work, we developed a dual-carbon-confined SnO2 nanocrystal anode (CNTs@SnO2@NC) designed for high-performance SIBs. This innovative structure uses carbon nanotubes (CNTs) and a nitrogen-doped carbon (NC) coating to stabilize SnO2, ensuring structural integrity during charge/discharge cycles. The CNTs network in CNTs@SnO2@NC can alleviate the agglomeration of SnO2 nanocrystals to a certain extent; With its superior electronic conductivity, CNTs can enhance the anode's conductivity and function as an electronic highway; The sodiophilic properties and good electrical conductivity of CNTs enable sodium ions to migrate rapidly on the surface of the nanotubes. Moreover, numerous external defects and active sites generated by nitrogen doping enhance the sodium ion absorption capabilities; The existence of nitrogen-doped carbon coating can effectively accommodate the volume changes of SnO2 and enhance the structural stability of CNTs@SnO2@NC composites during the repeated charge and discharge cycles. As a result, the CNTs@SnO2@NC composite demonstrates excellent electrochemical performance, achieving capacity of 235 mAh g−1 at 0.1 A g−1 over 100 cycles and 102 mAh g−1 at 1.0 A g−1 over 300 cycles. In a full-cell configuration with a Na3V2(PO4)3 cathode, it delivers 38 mAh g−1 at 100th cycle at 0.1 A g−1. This study underscores the substantial improvements achieved by dual-carbon confinement for high-performance SIB anodes, offering a promising direction for future anode material design.

Nanocrystal Agglomerates of Curcumin Prepared by Electrospray Drying as an Excipient-Free Dry Powder for Inhalation.

Curcumin has shown beneficial effects on pulmonary diseases with chronic inflammation or abnormal inflammatory responses, including chronic obstructive pulmonary disease, asthma, and pulmonary fibrosis. Clinical applications of curcumin are limited due to its chemical instability in solution, low water solubility, poor oral bioavailability, and intestinal and liver first-pass metabolism. Pulmonary delivery of curcumin can address these challenges and provide a high concentration in lung tissues. The purpose of the current work was to prepare a novel inhalable dry powder of curcumin nanocrystals without added excipients using electrospray drying (ED) with improved dissolution and aerosolization properties. ED of curcumin was performed at 2 and 4% w/v concentrations in acetone. Physicochemical properties of the formulated powders were evaluated by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), density and powder flow measurements, and in vitro dissolution. The in vitro deposition studies were conducted using next-generation impactor (NGI) and aerosol performance and aerodynamic particle size parameters were calculated for prepared formulations. ED could produce agglomerates of nanocrystals with a size of about 500 nm at an acceptable yield of about 50%. PXRD and FTIR data revealed that prepared nanocrystals were in a stable crystalline state. The bulk and tapped density of prepared agglomerates were in the range appropriate for pulmonary delivery. Formed nanocrystals could significantly improve the dissolution rate of water-insoluble curcumin. The optimized formulation exhibited acceptable recovered dose percentage, high emitted dose percentage, optimum mean mass median aerodynamic diameter, small geometric standard deviation, and high fine-particle fraction that favors delivery of curcumin to the deep lung regions. The ED proved to be an efficient technique to prepare curcumin nanocrystals for pulmonary delivery in a single step, at a mild condition, and with no surfactant.

Multifunctional Polymer Restraint of the Agglomeration of SnO2 Nanocrystals for Efficient and Stable Planar Perovskite Solar Cells.

The aggregation of SnO2 nanocrystals due to van der Waals interactions is not conducive to the realization of a compact and pinhole-free electron transport layer (ETL). Herein, we have utilized potassium alginate (PA) to self-assemble SnO2 nanocrystals, forming a PA-SnO2 ETL for perovskite solar cells (PSCs). Through density functional theory (DFT) calculations, PA can be effectively absorbed onto the surface of SnO2. This inhibits the agglomeration of SnO2 nanocrystals in solution, forming a smoother pinhole-free film. This also changes the surface contact potential (CPD) of the SnO2 film, which leads to a reduction in the energy barrier between the ETL and the perovskite layers, promotes effective charge transfer, and reduces trap density. Consequently, the power conversion efficiency (PCE) of PSCs with a PA-SnO2 ETL increased from 19.24% to 22.16%, and the short-circuit current (JSC) was enhanced from 23.52 to 25.21 mA cm-2. Furthermore, the PA-modified unpackaged device demonstrates better humidity stability compared to the original device.

Seed-assisted synthesis of Ga-MFI slabs and nanocrystal agglomerates and comparative study of acidic properties

A series of Ga-MFI zeolites were one-step synthesized following the seed-assisted strategy without using additional organic template. The effects of synthesis parameters on the framework fabrication, morphology evolution, and gallium incorporation were systematically investigated by XRD, N2-adsorption, UV-Raman, STEM, TEM, solid state NMR, NH3-TPD, and Py-IR analyses. The Si/Ga seed exhibited a highly efficient structure-directing capability in the assembly of MFI framework and the amount of the costly tetrapropylammonium hydroxide (TPA+) was thus decreased to less than one-tenth in comparison with the traditional synthesis. Crystallization temperature and pre-aging conditions played the key roles in the Ga-MFI zeolite synthesis. Both of the morphology and the intraframework gallium concentration can be facilely controlled by adding the mineralizer and surfactant. The addition of NH4F and CTAB was favorable for the formation of the slabs-form product but against to the gallium substitution. Only with the help of Si/Ga seed, the synthesized Ga-MFI nanocrystal agglomerates possess a highly accessible hierarchical mesopore structure that consisted solely of interparticle-type mesopores. Simultaneously, it also exhibited a remarkable gallium incorporation, which ensured the great acidic properties, including strong acidic strength and high acid amount. As a consequence, the Ga-MFI nanocrystal agglomerates performed the excellent catalytic activity in the LDPE degradation.

Synthesis, Characterization and Photocatalytic Activity of Spherulite-like r-TiO2 in Hydrogen Evolution Reaction and Methyl Violet Photodegradation

Synthesis and characterization of spherulite-like nanocrystalline titania with rutile structure (r-TiO2) are described herein. The r-TiO2 particles were synthesized via the convenient and low-cost hydrothermal treatment of TiO(C6H6O7) titanyl citrate. The r-TiO2 spherulites are micron-sized agglomerates of rod-shaped nanocrystals with characteristic sizes of 7(±2) × 43(±10) nm, oriented along (101) crystallographic direction, and separated by micropores, as revealed by SEM and TEM. PXRD and Raman spectroscopy confirmed the nanocrystalline nature of r-TiO2 crystallites. BET analysis showed a high specific surface area of 102.6 m2/g and a pore volume of 6.22 mm3/g. Photocatalytic performances of the r-TiO2 spherulites were investigated for the processes of methyl violet (MV) degradation in water and hydrogen evolution reaction (HER) in aqueous solutions of ethanol. The (MV) degradation kinetics was found to be first-order and the degradation rate coefficient is 2.38 × 10−2 min−1. The HER was performed using pure r-TiO2 spherulites and nanocomposite r-TiO2 spherulites with platinum deposited on the surface (r-TiO2/Pt). It was discovered that the r-TiO2/Pt nanocomposite has a 15-fold higher hydrogen evolution rate than pure r-TiO2; their rates are 161 and 11 nmol/min, respectively. Thus, the facile synthesis route and the high photocatalytic performances of the obtained nanomaterials make them promising for commercial use in such photocatalytic processes as organic contamination degradation and hydrogen evolution.

Rheology of nanocrystal-bearing andesite magma and its roles in explosive volcanism

Recent petrological and experimental studies have proposed that explosive volcanism may originate from the formation of nanoscale crystals in magma and the resultant ductile–brittle transition. However, the rheology of magma with quantified volume fractions of nanoscale crystals has not been investigated before, and thus, the formation of nanoscale crystals causing magma fragmentation that explains the origin of explosive eruptions is not conclusive. Here, we investigate the rheology of andesite magma with nanoscale crystals (magnetite). For this, a glass fibre elongation experimental apparatus with a heating furnace was developed at the synchrotron radiation X-ray system (SPring-8). During melt elongation, we observed the formation of crystals using small-angle X-ray scattering and wide-angle X-ray diffraction. Our experimental data demonstrate that magma viscosity increases with the formation of nanoscale crystals, but the degree of the increase is much lower than that predicted from analogue materials. Finally, we conclude that nanocrystal formation in intermediate composition magmas cannot explain rheological transition and other mechanisms such as nanocrystal agglomeration (not observed in our experiments) and/or heterogeneous nucleation of gas bubbles on nanocrystals are required to induce mafic to intermediate explosive volcanisms.

(Digital Presentation) Controllable Preparation of Ultrasmall Pt-Based Intermetallic Nanocrystals Via Atomic Layer Deposition for Hydrogen Fuel Cell

The cost and endurance anxiety about proton exchange membrane fuel cells (PEMFCs) has prompted the rapid development of platinum-based (Pt-based) oxygen reduction electrocatalysts towards smaller particle sizes, higher durability and alloying. However, well-balanced these advanced trends by a simple approach is difficult in practice, because the existing solutions are problematic in removing the protective organic coating or oxide shell that preventing the high-temperature agglomeration of Pt-based nanocrystals, or broadening the size range of Pt-based nanocrystals which caused by the heterogeneous distribution of heteroatom anchor points on supports. With a self-developed strategy that based on the atomic layer deposition (ALD), we have addressed these problems in two aspects. One is directly loading size and distribution controllable Pt nanocrystals on diverse supports, and another is indirectly depositing easily removed ultra-thin metal oxide coating with dual functions on prefabricated ultrasmall Pt nanocrystals to restrain their sintering effect during high temperature ordering. By controlling the temperature and pulse time of ALD, we successfully synthesized ultrasmall (< 2 nm) Pt nanocrystals on surface inactive TiC nanoparticles and nanowires. These two new electrocatalysts exhibited comparable oxygen reduction activity and durability on par with commercial Pt/C with lower Pt loading. And using this strategy, about 1 nm ZnO coating on Pt nanocrystals was performed to construct uniform PtZn intermetallic nanocrystals with the ultrasmall size of 2.50 ± 0.65 nm and excellent stability for oxygen reduction reaction. The mass activity of PtZn intermetallic nanocrystals reaches to 0.60 A mgPt -1 at 0.9 V (6 times than commercial Pt/C) and only 13 mV decrease of half-wave potential after 30000 cycles of accelerated durability testing rivaling the most recently reported PtZn catalysts. Ultrasmall sizes and excellent features of our Pt and Pt-based intermetallic nanocrystals are all attributed to the accurate control of ALD and could be a promising method applying to other Pt-based intermetallic nanocrystals.

In-situ construction of vacancies and schottky junctions in nickel-iron selenide within N-graphene porous matrix for enhanced sodium/potassium storage

The exploration of suitable anode materials to overcome key issues of electrode volume fluctuation and sluggish electronic/ionic transport dynamics caused by the large radius of sodium/potassium ions is an urgent need for energy storage. Herein, a heterogenetic nickel-iron selenide containing vacancies and schottky junctions within N-graphene porous matrix to realize external and internal charge transport is constructed via a one-pot in-situ carbonization and selenization route. In the composite, the iron selenide possessing metallic property acts as the conductor incorporated with nickel selenide semiconductor for constructing schottky junctions and vacancies to induce internal charge transfer and transport of the active material, and the N-graphene not only enhance the interparticle conductivity by bridging the selenides, but also relieve the volume fluctuation and keep integrity without agglomeration of nanocrystals. Profiting from the synergistic effect, the material exhibits boosted electrochemical properties for sodium (264 mA h g−1 after 1000 cycles at 1.0 A g−1) and potassium (115 mA h g−1 after 500 cycles at 0.5 A g−1) storage. And the thorough understanding of electrochemical mechanism on the raised performance is explicitly interpreted by combining ex-situ characterization results and density functional theoretical calculations.

ZIF-8 derived ZnO–calcium silicate mesoporous structures: Synthesis and photocatalytic activity

Nanoscale metal-organic frameworks (MOFs) show potential as catalysts or catalyst precursors, but they suffer from difficult separation and weak stability and do not conform to practical application conventions. Herein, we demonstrate the application of nanostructured calcium silicate hydrate (C–S–H), the building block of Portland cement concrete, to fabricate hierarchically porous zeolitic-imidazolate-framework-8 (ZIF-8)-derived ZnO nanocomposites. The dispersing and stabilizing effects of the C–S–H nanoplate structure effectively suppressed the agglomeration of ZIF-8 nanocrystals during high-temperature treatment. After calcination at 450 °C, ZnO nanocomposites with high specific surface area (579 m 2 g −1 ) and hierarchical porosity were obtained. The nanocomposites were used as photocatalysts for degradation of rhodamine B and exhibited degradation efficiency as high as 95.5% within 45 min of UV light illumination with high photocatalytic stability and excellent reusability. This study demonstrated a facile way of using economic and versatile C–S–H nanostructures to fabricate MOF and MOF-derived nanocomposites with enhanced stability and functionality. •The synthesis of MOF-derived ZnO supported on environment-friendly C–S–H is reported. •The nanocomposites presented a high specific surface area (579 m 2 g −1 ) and hierarchical porosity. •High photocatalytic activity and excellent stability and reusability were achieved. •The study opens a new route for the synthesis of green MOF-derived nanostructured composites.

Pomegranate-like structured Nb2O5/Carbon@N-doped carbon composites as ultrastable anode for advanced sodium/potassium-ion batteries

The distinctive pomegranate-like Nb2O5/Carbon@N-doped carbon (Nb2O5/C@NC) composites are fabricated using hydrothermal method integrated with nitrogen doped carbon coating procedure. For the SIBs anode, the Nb2O5/C@NC composites present superior rate character and sustainable capacity (117 mAh g−1 upon 1000 cycles at 5 A g−1). The in-situ X-ray diffraction (XRD) is utilized to research its sodium storage mechanism. Furthermore, for PIBs, the Nb2O5/C@NC composites present sustainable capacity (81 mAh g−1 upon 1000 cycles at 1 A g−1). The outstanding performance of Nb2O5/C@NC composites is ascribed to its unique architecture, in which Nb2O5 nanocrystals embedded in porous carbon can restrain agglomeration of Nb2O5 nanocrystals, enhance electron/ion diffusion kinetics, and ensure electrolyte accessibility, and moreover, NC shell layer can provide effective active sites and further increase ions/electrons transfer.

Seed-Assisted Synthesis of Ga-Mfi Slabs and Nanocrystal Agglomerates and Comparative Study of Acidic Properties

Seed-Assisted Synthesis of Ga-Mfi Slabs and Nanocrystal Agglomerates and Comparative Study of Acidic Properties

Preparation of HKUST-1/PEI mixed-matrix membranes: Adsorption-diffusion coupling control of small gas molecules

HKUST-1 nanocrystals (50–80 nm) were homogeneously dispersed in a polyetherimide (PEI) polymer matrix. The use of a capping agent (sodium formate) prevented the agglomeration of HKUST-1 nanocrystals in the casting solution. The highly dispersed HKUST-1 nanocrystals were found to strengthen the interactions with the PEI and minimize the interfacial holes by providing more accessible Cu unsaturated metal sites for the CO bonds on the five-membered rings of the PEI matrix. The PEI membrane loaded with 30 wt % HKUST-1 nanocrystals (30-N-HKUST-1/PEI) showed a high H2 permeability (193.3 Barrer at 25 °C under 1.5 bar) and good ideal H2/CH4 and H2/CO2 selectivity factor of 101.7 and 20.6 in a single gas test, respectively. In the gas mixture test, it also showed a good separation performance, i.e., a H2/CH4 and H2/CO2 selectivity factor of 82.4 and 16.5 was measured, respectively. The 30-N-HKUST/PEI membrane was tested in a gas mixture at different temperatures (25–100 °C), different pressures (0–3 bar) and various time (5–72 h) to study the performance in more realistic conditions thus to be further considered in the separation of syngas.

Nanocomposites of PVA/cellulose nanocrystals: Comparative and stretch drawn properties

AbstractPolyvinyl alcohol (PVA) nanocomposites were made using two different cellulose nanocrystals (CNCs). Sugarcane bagasse‐based CNC and a commercial CNC were used in preparing nanocomposites. Both types of nanocomposites were prepared by solution casting method at 5 wt% CNC. PVA and nanocomposites films were also stretch‐drawn four times to study the nature of reinforcement by two different CNCs. Fourier transform infrared spectroscopy was used to examine functional group characteristics. Nanocomposite morphology and crystalline structures were analyzed using a scanning electron microscope and X‐ray diffraction, respectively. Thermogravimetric analysis and differential scanning calorimetry were used to study thermal properties. Tensile properties were used to study mechanical properties. Commercial CNC reinforcement improves the tensile properties of PVA. However, laboratory CNC reinforcement decreases the tensile properties of PVA due to nanocrystal agglomeration and uneven dispersion. All stretch‐drawn nanocomposite films showed a significant increase in tensile strength and modulus values at the expense of strain at break. Water absorption of PVA/commercial CNC nanocomposites was slightly higher than that of pure PVA.

Improvement of Drug-Loading Properties of Hydroxyapatite Particles Using Triethylamine as a Capping Agent: A Novel Approach

Particles that modify delivery characteristics are a focus of drug-loading research. Hydroxyapatite particles (HAPs) have excellent biocompatibility, shape controllability, and high adsorption, making them a potential candidate for drug-delivery carriers. However, there are still some defects in the current methods used to prepare HAPs. In order to avoid agglomeration and improve the drug-loading properties of HAPs, the present study provides a novel triethylamine (TEA)-capped coprecipitation template method to prepare HAPs at room temperature. In addition, pure water and anhydrous ethanol were used as solvents to investigate the capping effect of the small-molecule capping agent TEA during the synthesis of HAPs. The results showed that the HAPs prepared in the TEA ethanol system had a smaller particle size (150–250 nm), better dispersion and higher crystallinity. The results were significantly different from those of the conventional preparation methods without TEA. However, the hydroxyapatite crystal would agglomerate to a certain extent after being stored for a period of time, forming micro/nano-sized agglomerates of nanocrystals. FITR analysis and SEM observation showed that the capping effect of TEA promoted the formation of a smaller template and dispersed HAPs were quickly formed by dissolution and reprecipitation processes. The drug-loading experiments showed that the HAPs prepared in the TEA ethanol system had high drug-loading capacity (239.8 ± 13.4 mg·g−1) as well as an improved drug-release profile demonstrated in the drug-release experiment. The larger specific surface area associated with the smaller particle size was beneficial to the adsorption of drugs. After drying at 60 °C, TEA was evaporated from the HAPs which agglomerated into larger micron particles with more drug encapsulated. Thus, the effect of a sustained release was achieved. In the present research, a novel approach was developed by using triethylamine as the capping agent to prepare micro/nano-sized agglomerates of HAP nanocrystals with improved drug loading, which is predicted to have potential application in drug delivery.

Near-infrared photoluminescence and micro-Raman study of spark discharge germanium nanoparticles

We report the investigation of near-infrared (NIR) photoluminescent and structural properties of aerosol germanium nanoparticles, synthesized by spark discharge method followed by sintering in a tube furnace at different temperatures varying from 25 to 750 °C. We demonstrate a growth of mean primary particle size and change in morphology from agglomerates of germanium nanocrystals in amorphous matrix to individual pure crystal germanium nanoparticles with temperature increase. Pure germanium nanoparticles were prepared at temperatures above 600 °C and distinguished by absence of near-infrared photoluminescence. According to Raman spectroscopy the presence of amorphous germanium in the samples, sintered at 25 to 450 °C, leads to appearance of the luminescence in infrared region with intensity increase from 1100 to 1550 nm.

Agglomeration of cellulose nanocrystals: the effect of secondary sulfates and their use in product separation

This study was aimed at the development of a better understanding of the agglomeration behavior of sulfated cellulose nanocrystals (CNCs) in the presence of sulfates with monovalent (NH4+, K+, Na+) and divalent (Ca2+) cations, and to demonstrate their potential in simple and efficient product separation. Protonated CNCs were counterion-exchanged and their ionic strength was increased by adding sulfates of the respective cation to trigger agglomeration. The critical concentrations of agglomeration (CAC) and peptization (CPC) were determined. We found that the agglomeration behavior of CNCs could be attributed to matching affinities between the cations and the sulfate half-ester groups on the CNC surfaces. Based on these findings, a facile and efficient downstream process was designed to separate CNCs from neutralized reactant solutions using CAC and CPC. This method provides colloidally stable CNCs at high yield provided by centrifugation. When salt concentrations in the product are maintained below the CAC, as prepared CNCs from neutralized reactant solutions might be used in hydrogels and emulsions.

Efficient synthesis of Cu3P nanoparticles confined in 3D nitrogen-doped carbon networks as high performance anode for lithium/sodium-ion batteries

As a metal phosphide, copper phosphide (Cu3P) offers the advantages of low-cost, environmental friendliness, and excellent volumetric capacity. However, the development of Cu3P in lithium/sodium-ion batteries is limited by its poor conductivity, large volume change, and nano-crystal agglomeration. In this work, we prepared nano-scale Cu3P uniformly embedded in a nitrogen-doped three-dimensional (3D) porous carbon network (denoted as Cu3P/N-CN) through a simple and novel strategy of freeze-drying with NaCl crystals as template. The Cu3P nanoparticles effectively alleviated the physical strain generated during the charging and discharging processes and improved the utilization rate of the active material. Moreover, the 3D porous structure enhanced the conductivity, inhibited the agglomeration of the Cu3P nanoparticles, and facilitated the rapid diffusion of electrons/ions. The Cu3P/N-CN composite anode exhibited an outstanding rate capability (431.6 mAh g−1 at 3.0 A g−1), outstanding cyclic stability (752.3 mAh g−1 at 0.1 A g−1 over 100 cycles) for lithium storage, and excellent rate performance (220.0 mAh g−1 at 3.0 A g−1) and cycle performance (340.9 mAh g−1 at 0.1 A g−1 over 100 cycles) for sodium storage. This novel Cu3P/N-CN electrode thus has a promising application in energy storage technologies.

Urea–nitrate combustion synthesis of CuO/CeO2 nanocatalysts toward low-temperature oxidation of CO: the effect of Red/Ox ratio

The low-temperature catalytic oxidation of carbon monoxide (CO) is the key process to overcome incomplete combustion of fossil fuels for both commercial (e.g., lowering automotive emissions) and domestic (e.g., indoor air quality improvement) applications. So the development of cost-effective and high-active catalysts made from non-noble metals is an actual material science challenge. Ce–Cu–O oxide system is one of the most prospective to investigate due to the feasibility of the Langmuir–Hinshelwood dual-site oxidation mechanism, and, in our previous work, it was shown that solution combustion synthesis using the urea as fuel in stoichiometric ratio with metal nitrates is a most reasonable fuel choice toward the synthesis of CuO/CeO2 nanocatalysts for effective CO oxidation. In this work, the effect of the Red/Ox (urea to nitrates or U/N) ratio on the catalytic oxidation activity of resulting CuO/CeO2 composites is in the spotlight. Series of CuO/CeO2 nanocatalysts were successfully synthesized via the urea–nitrate combustion method with U/N ratios from 0.2 to 1.4 and then were applied for CO oxidation. The samples before and after catalysis were characterized by EDX, SEM, PXRD, N2-ASA, H2-TPR, etc. It was shown that the U/N ratio strongly affects the qualitative and quantitative X-ray phase composition (c-CeO2, m-CuO, and am-CuO, in general), CeO2 and CuO crystallite sizes (4.9–63.0 nm and 14.7–28.3 nm, correspondently), specific surface area (4–46 m2/g) and porosity (0.009–0.033 cm3/g), as well as the morphology of nanocomposites and their catalytic characteristics (t50% = 113–199 °C and t100% = 137–348 °C). The sample synthesized at U/N = 0.2 shows the best oxidative performance (t50% = 113 °C and t100% = 137 °C) explained by the highest surface (46 m2/g), the lowest CeO2 crystallite size (4.9 nm), and the lowest degree of agglomeration of nanocrystals in the CuO/CeO2 composite. Besides, cyclic and water resistivity tests of this sample confirm the high stability of its catalytic activity in the CO oxidation process due to the close conjugation of the CeO2 and CuO components in the resulting nanocomposite, confirmed by the H2-TPR analysis results. Thus, it was shown that the optimization of Red/Ox ratio in the urea–nitrate combustion process contributes to obtaining the stable CuO/CeO2 nanocatalyst with gradual conversion of CO at quite low temperatures (ti ~ 50 °C). We believe that the subsequent reduction of CuO loading in the Ce–Cu–O system allows creating a cost-effective and stable composite nanocatalyst with high activity even at room temperature.

Facile growth and re-crystallization of polymer-based inorganic-organic 2D hybrid composites and their applications

The in-situ growth and recrystallization of inorganic-organic (IO) hybrids within the natural free volume of polymer matrices for the realization of significantly stable IO hybrid-polymer composites and its applications have been presented. A general strategy is explored to attain uniform and facile growth of IO hybrid nanocrystals (2–3 nm) within the interstitial spaces of polymer matrix. Annealing further supports the agglomeration and self-assembly of nanocrystals into highly c-oriented hexagonal microplatelets of ∼10–20 μm2 and 50–100 nm thickness within the polymer matrix. The resultant composites endow highly luminescent retaining the typical thermally and mechanically stable polymeric nature. Series of optical, structural, morphological and thermal studies are performed to understand the growth conditions and uniform distribution of IO nanocrystallites within the polymer. To exemplify, LED colour conversion using encapsulation/surface coating and polymeric blocks fabrication for optical waveguide/channel inscription are demonstrated to foresee many new flexible and robust applications. Thus, the present approach offers a new paradigm to achieve light-emitting IO hybrids in the form of polymeric composites for advanced optoelectronic device applications.

Morphology adjustment of ZSM-5 nanocrystal agglomerates and achievement of improved activity in LDPE catalytic cracking reaction

Abstract The cuplike ZSM-5 nanocrystal agglomerates were directly synthesized following an organic template-free strategy with the assistance of a preformed MFI precursor (the seed solution) and a nonionic-type polyacrylamide (PAM), which play the roles of nucleation promotion and crystal growth restriction, respectively. The morphological adjustment approach, hierarchical mesopore structure evolution, and the derived acidic properties of the resulting ZSM-5 nanocrystal agglomerates were systematically investigated. The cuplike agglomerates possessing a thin-wall structure which is composed of monolayer ZSM-5 nanocrystals can be synthesized by simply prolonging the high-temperature (448 K) crystallization. Due to the morphological characteristics, the diffusion pathway in the resulting cuplike ZSM-5 nanocrystal agglomerates (CZNA) is perpendicular to the cup wall and the length is identical to the wall thickness, around 200 nm. As for the formation of the cuplike morphology, the MFI composition building units (CBU) in the center nanocrystals continuously dissociate, migrate, rearrange, and assemble onto the nanocrystals close to the external surface of the preformed agglomerates, thereby forming a “shell-like” structure. After random collapse takes place on the “shell” through prolonging the high-temperature hydrothermal treatment, a cuplike morphology is obtained. As the consequence, the CZNA simultaneously possesses a high crystallinity and a highly open mesostructure, especially as well as the extremely short diffusion pathway. Because of these advantages, CZNA exhibits very high catalytic activity in the Low Density Polyethylene (LDPE) catalytic cracking reaction.