Decrease In Degree Of Crystallinity Research Articles

Improving the optical, thermal, mechanical, electrical properties and antibacterial activity of PVA-chitosan by biosynthesized Ag nanoparticles: Eco-friendly nanocomposites for food packaging applications

In this study, nanocomposite films were produced by blending polyvinyl alcohol (PVA) and chitosan (Cs) polymers with 70 % PVA and 30 % Cs, incorporating silver nanoparticles (Ag NPs) via a solution-casting method. The research aims to investigate the impact of the biosynthesized Ag NPs by Chenopodium murale leaf extract on optical, morphological, mechanical, thermal, electrical, and antibacterial properties. XRD analysis showed a decrease in crystallinity degree with Ag NPs addition. TEM revealed Ag NPs in cubic and spherical shapes with an average size of 23.4 nm. SEM and AFM indicated surface morphology changes. FT-IR spectra showed interaction between Ag ions and the blend. The energy gap decreased with increasing Ag NPs concentration. TGA exhibited enhanced thermal stability. Mechanical properties improved significantly. AC electrical conductivity and dielectric parameters were studied. Antibacterial activity against Gram-positive and Gram-negative bacteria was observed. Overall, PVA/Cs-Ag NPs films show promise for food packaging and optoelectronic applications.

The Effect of Isoniazid–Maltitol Solid Dispersions on Aqueous Solubility and Permeability

Maltitol (MAL) is a well-known polyol with potential pharmaceutical applications. Unlike other polyols, its utilization as a carrier for solid dispersions (SDs) has not been adequately investigated. This research studied the feasibility of MAL as an SD carrier to enhance the biopharmaceutical properties of a BCS class I/III drug, isoniazid (INH). SDs of INH–MAL were prepared by the fusion method, and physicochemical characteristics were investigated to determine the solid-state habit, solubility and permeation enhancement of INH. Fourier-transform infrared (FT-IR) spectroscopy demonstrated significant peak broadening for the SDs consisting of a higher MAL concentration. Powder X-ray diffraction indicated a decrease in degree of crystallinity with increasing MAL concentration. Hot-stage microscopy (HSM) and scanning electron microscopy (SEM) revealed that INH–MAL molar ratios affect the type of SD prepared via the fusion method. Results from the equilibrium solubility studies indicated significant INH solubility improvement (p < 0.05) with SDs in comparison with the pure drug and physical mixtures. The artificial membrane permeation assay (PAMPA) of INH was positively affected by the presence of MAL. The results of the study indicated the potential for MAL as a carrier in the preparation of SDs for the solubility and/or permeability enhancement of drugs.

The evaluation of in vitro antichagasic and anti-SARS-CoV-2 potential of inclusion complexes of β- and methyl-β-cyclodextrin with naphthoquinone.

The compound 3a,10b-dihydro-1H-cyclopenta[b]naphtho[2,3-d]furan-5,10-dione (IVS320) is a naphthoquinone with antifungal and antichagasic potential, which however has low aqueous solubility. To increase bioavailability, inclusion complexes with β-cyclodextrin (βCD) and methyl-β-cyclodextrin (MβCD) were prepared by physical mixture (PM), kneading (KN) and rotary evaporation (RE), and their in vitro anti-SARS-CoV-2 and antichagasic potential was assessed. The formation of inclusion complexes led to a change in the physicochemical characteristics compared to IVS320 alone as well as a decrease in crystallinity degree that reached 74.44% for the IVS320-MβCD one prepared by RE. The IVS320 and IVS320-MβCD/RE system exhibited anti-SARS-CoV-2 activity, showing half maximal effective concentrations (EC50) of 0.47 and 1.22μg/mL, respectively. Molecular docking simulation suggested IVS320 ability to interact with the SARS-CoV-2 viral protein. Finally, the highest antichagasic activity, expressed as percentage of Tripanosoma cruzi growth inhibition, was observed with IVS320-βCD/KN (70%) and IVS320-MβCD/PM (72%), while IVS320 alone exhibited only approximately 48% inhibition at the highest concentration (100μg/mL).

Zircon texture and composition fingerprint HREE enrichment in muscovite granite bedrock of the Dabu ion-adsorption REE deposit, South China

More than 90% of the global heavy rare earth elements (HREE) supply is currently from the ion-adsorption REE deposits in South China. However, the mechanism of HREE enrichment in granite bedrock of REE mineralized weathering crusts remains poorly understood. In this study, we present a comprehensive investigation on zircon texture and composition as a proxy to unravel the magmatic-hydrothermal processes which resulted in HREE enrichment of the Dabu muscovite granites. Our results show that zircon in the Dabu muscovite granites can be classified into three types based on morphology, internal structure and chemical compositions. The early-magmatic zircon grains (ZrnI) are prismatic crystals with bright oscillatory zoning, and crystallized early in the granitic magma. The late-magmatic zircon grains (Zrn-II) occur as murky euhedral or subhedral crystals or as overgrowth on ZrnI, and crystallized from a volatile-enriched residual melt in the late magmatic stage. The hydrothermal zircon (Zrn-III) is anhedral without oscillatory zoning, possibly formed via intense hydrothermal alteration of Zrn-II in the hydrothermal stage. Raman spectra show a decrease in degree of crystallinity from Zrn-I to Zrn-III. In-situ compositional and isotopic analyses suggest that zircon geochemistry is a good proxy for the magmatic-hydrothermal processes of the host granite. Zircon UPb dating yields similar ages of 155.3 ± 1.4 Ma (2σ) and 154.1 ± 1.0 Ma (2σ) for Zrn-I and Zrn-II, respectively. The decrease of Zr/Hf from Zrn-I to Zrn-III indicates that the Dabu muscovite granites underwent magmatic to hydrothermal evolution. Furthermore, the decreasing δ18O values of Zrn-I to Zrn-III suggest the increasing involvement of meteoric water in the fluids. Significantly, compared with Zrn-I and Zrn-II, Zrn-III has the highest U, Hf and REE, in particular HREE. The LREE/HREE ratios decrease with the increase of REE contents and the decrease of Zr/Hf ratios from early to late zircon of the granite bedrock of ion-adsorption HREE deposits, which is significantly different from those of carbonatite-alkaline related REE deposits. The significant increase of HREE concentrations in early to late zircon should be ascribed to the introduction of HREE-rich fluids during magma evolution. Therefore, we propose that the HREE-rich fluids from magma exsolution metasomatized the granites to achieve further enrichment of HREE, which is an important prerequisite for the formation of ion-adsorption HREE deposits. Accordingly, we argue that zircon composition can be used as a chemical indicator for the REE behaviors in magmatic-hydrothermal systems that are vital to the formation of REE deposits.

Sulphate-substituted tricalcium phosphate β-TCP: Effect of SO42− insertion and microwave conditions

In the present work, we have successfully synthesized pure β-TCP and sulphate substituted β-TCP by a wet chemical method derived microwave irradiation technique. XRD and FTIR results showed that the insertion of the SO42− group at PO43− sites, without microwave treatment, decreases the crystallinity of β-TCP samples and promotes the growth of calcium pyrophosphate β-CPP as a secondary phase. Our results also showed that wet chemical preparation combined with microwave treatment for TCPS-M led to a decrease in peak intensity, crystallite size average, as well as the peak broadening, confirming the decrease in degree of crystallinity. The average crystallite size of samples decreases from 46 to 21 nm. Besides, we noted a slight shift of XRD peaks towards a lower diffraction angle, which could be explained by the replacement of PO43− ions, with a smaller anionic radius of 0.238 nm, by SO42− ions with larger anionic radius of 0.258 nm. The FTIR analysis revealed the presence carbonate groups and the formation of β-CPP as a secondary phase for sulphate substituted β-TCP, confirming the XRD results. The Ca/P molar ratios were calculated using the ICP/AES technique. Furthermore, the SEM micrograph of SO42− substituted β-TCP demonstrates the deposition of β-CPP on β-TCP surface, supporting the XRD and FTIR results. These results emphasize that microwave irradiation and insertion of SO42− in the β-TCP matrix affect the degree of crystallinity and increase structural disorder.

Investigation of the doping mechanism and electron transition bands of PEO/KMnO4 complex composite films

Polyethylene oxide (PEO) incorporated with potassium permanganate (KMnO4) was prepared using the solution casting technique forming PEO/KMnO4 complex composite films. The physicochemical properties, doping mechanism, and electron transition bands of PEO/KMnO4 were investigated. Introducing KMnO4 PEO matrix led to a decrease in crystallinity degree and optical bandgap energy due to the creation of polarons and bipolarons that form new energy levels in the bandgap between the HOMO and LUMO; in addition, to form of a new transition band appears at about 380 nm is attributed to the n{-}{pi }^{*} electronic transitions are generated due to the unsaturated center of the molecules. The existence of KMnO4 in the polymer matrix leads to the blocking of light in the 250–400 nm range. Consequently, PEO/KMnO4 complex composite films could be used as UV-light shielding filters. Furthermore, the electrical conductivity of the PEO/KMnO4 complex composite films increases as KMnO4 concentration is increased in the PEO matrix since the created new energy levels in the bandgap between the HOMO and LUMO can be populated with conduction electrons providing true ohmic conduction with the delocalization of the electron densities moving on the polymer chain.

The Influence of High-Intensity Ultrasonication on Properties of Cellulose Produced from the Hop Stems, the Byproduct of the Hop Cones Production.

The goal of this work is to evaluate the hop stems, a byproduct of hop cones production, as a potential source of cellulose. Hop stems contain up to 29% of cellulose. The cellulose isolation was conducted through the thermochemical treatment. After high-speed blending, the cellulose was characterized by 67% of crystallinity degree obtained from X-ray diffraction and median diameter of 6.7 nm obtained from atomic force microscopy imaging. The high-intensity ultrasonication (HIUS) was applied to reach further disintegration of cellulose fibers. The longer HIUS treatment resulted in decrease in crystallinity degree even up to 60% and decrease in the fiber diameter up to 4 nm. The Fourier transform infrared spectroscopy (FTIR) spectra showed that HIUS treatment led to changes in intermolecular hydrogen bonds. The stability of cellulose dispersions versus length of HIUS treatment was monitored over 14 days with back dynamic light scattering and laser Doppler electrophoresis methods. Obtained results are evidence that the hop stems are a potential source of cellulose and that it is possible to obtain stable dispersions after HIUS treatment. This was the first time that the properties of hop cellulose have been described so extensively and in detail after the use of HIUS treatment.

PA6/PA66/talc composite: Effect of reprocessing on the structure and properties

AbstractIn this study the effect of repeated injection molding cycles on the structure and properties of polyamide 6/polyamide 66/talc (PA6/PA66/talc ‐ 35/35/30) composite was investigated for samples subjected to one, four, and seven processing cycles. Their morphology (scanning electron microscopy), structure (Fourier transform infrared spectroscopy), melt viscosity (melt flow index [MFI]), mechanical (tensile, flexural, impact, and fatigue tests), and thermal properties (differential scanning calorimetry and thermogravimetric analysis tests) were analyzed. The increase in MFI value and the decrease in the maximum decomposition temperature of PA6, observed by TG analysis, for samples subjected to seven processing cycles, indicated a possible reduction in molar mass of the PA6/PA66 matrix. These samples presented a decrease in degree of crystallinity of PA6 and PA66, which was more pronounced for PA6. The reprocessing of the composite did not present changes in the mechanical properties up to the fourth processing cycle, except for fatigue life which presented a 59% reduction. Samples subjected to seven processing cycles presented a decrease in tensile and flexural strength as well as in tensile and flexural modulus. Charpy impact strength of the samples did not significantly change upon reprocessing. The micrographs of the fatigue fractured surfaces indicated that the weak talc‐matrix interaction and talc‐matrix debonding became more evident with increasing processing cycles.

Pyrene-Benzimidazole Derivatives as Novel Blue Emitters for OLEDs.

Three novel small organic heterocyclic compounds: 2-(1,2-diphenyl)-1H-benzimidazole-7-tert-butylpyrene (compound A), 1,3-di(1,2-diphenyl)-1H-benzimidazole-7-tert-butylpyrene (compound B), and 1,3,6,8-tetra(1,2-diphenyl)-1H-benzimidazolepyrene (compound C) were synthesized and characterized for possible applications as blue OLED emitters. The specific molecular design targeted decreasing intermolecular aggregation and disrupting crystallinity in the solid-state, in order to reduce dye aggregation, and thus obtain efficient pure blue photo- and electroluminescence. Accordingly, the new compounds displayed reasonably high spectral purity in both solution- and solid-states with average CIE coordinates of (0.160 ± 0.005, 0.029 ± 0.009) in solution and (0.152 ± 0.007, 0.126 ± 0.005) in solid-state. These compounds showed a systematic decrease in degree of crystallinity and intermolecular aggregation due to increasing steric hindrance, as revealed using powder X-ray diffraction analysis and spectroscopic studies. An organic light-emitting diode (OLED) prototype fabricated using compound B as the non-doped emissive layer displayed an external quantum efficiency (EQE) of 0.35 (±0.04)% and luminance 100 (±6) cd m−2 at 5.5 V with an essentially pure blue electroluminescence corresponding to CIE coordinates of (0.1482, 0.1300). The highest EQE observed from this OLED prototype was 4.3 (±0.3)% at 3.5 V, and the highest luminance of 290 (±10) cd m−2 at 7.5 V. These values were found comparable to characteristics of the best pure blue OLED devices based on simple fluorescent small-molecule organic chromophores.

Epoxidized cardanol-based prepolymer as promising biobased compatibilizing agent for PLA/PBAT blends

Epoxidized cardanol-based prepolymer (ECP) generated from cashew nut shell liquid (CNSL) was successfully used as biobased compatibilizer/chain extender for poly (lactic acid) (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) (80:20 wt%) blends. The reactive compatibilization effectiveness of different amounts of this biobased additive was compared with that of a petroleum-derived glycidyl-based copolymer, namely Joncryl ADR4300 (ADR) in term of mechanical, dynamic-mechanical and thermal properties, as well as rheological and morphological aspects. The addition of 3 wt% of ECP resulted in significant improvement of yield stress, elongation at break, Young modulus and toughness. The results obtained with this additive were similar or even superior to those observed for ADR. A sea-island-type morphology with very small PBAT domains was also reached with the compatibilization, as indicated by scanning electron microscopy (SEM). The compatibilization was also suggested from the slight increase of the glass transition temperature of the PBAT phase and also a decrease in crystallinity degree of PLA phase. The results presented in this work open new possibilities for developing cost-effective biobased and/or biodegradable materials for food packaging applications.

In situ functionalization of poly(butylene adipate-co-terephthalate) polyester with a multi-functional macromolecular additive

Poly(butylene adipate-co-terephthalate) (PBAT) has been functionalized with Pluronic F127 as a secondary diol monomer by melt polycondensation. The variation of Pluronic content to max 12.2 wt% in the copolymer is investigated on microstructure analysis, molecular weight distribution, thermal properties, crystallinity, and thermo-responsive behavior. The microstructure in the Pluronic F127-functionalized PBAT (PPBAT) copolymer indicates that the amount of Pluronic unit which is attached to the PPBAT copolymers found to be increased from 5.9 to 9.1 to 12.2% (wt) with the feeding amount of 1.0 to 2.0 to 3.0 mmol, respectively. The weight average molecular weight has also found to increase from 23,555 to 43,841 g/mol in the PPBAT copolymers. The lowering of glass transition temperature has been also observed in the thermal analysis that indicates the improvement of the plasticization effect in the PPBAT copolymers with the increase of Pluronic from 0 to 12.2% (wt). Moreover, the crystallization behavior also indicates the disappearance of crystallization temperature and the appearance of cold crystallization temperature before melting with the increase of Pluronic content. The X-ray diffraction analysis further signifies the decrease in degree of crystallinity with an increase of Pluronic in PPBAT copolymers. The PPBAT copolymers display thermo-responsive behavior under physiological conditions due to the attachment of Pluronic comonomer onto the structural backbone.

Solid Dispersions of Famotidine: Physicochemical Properties and In Vivo Comparative Study on the Inhibition of Hyperacidity

AbstractFamotidine is a potent histamine 2 antagonist used in the treatment of gastric acid overproduction. Famotidine belongs to Class IV in Biopharmaceutics Classification System (BCS) which has low solubility and membrane permeability. The purpose of this study was to compare the solubility and dissolution profile of solid dispersions (SDs) of famotidine with mannitol (SD‐MAN) and with hydroxypropyl methylcellulose (SD‐HPMC), and to comparatively study their in vivo effectiveness against hyperacidity. Famotidine SDs were prepared by cogrinding technique with the respective carriers in various ratios and grinding time. SDs with the best solubility underwent dissolution rate studies, solid‐state characterization, and in vivo efficacy evaluation. The in vivo evaluation was conducted in Sprague Dawley rats receiving famotidine formulations in the dose equivalent to 12 mg/kg of famotidine. The study found that the famotidine SDs could greatly improve the solubility of famotidine by 100.61 and 120.91% for SD‐MAN and SD‐HPMC, respectively. The solid‐state characterization revealed the decrease in crystallinity degree of famotidine solid dispersion systems. The comparative study on the in vivo efficacy of famotidine SDs showed that SD‐HPMC was significantly better than SD‐MAN. This study concludes that SDs can improve the solubility and in vivo effectiveness of famotidine in overproduction of gastric acid.

Control of structural parameters and thermal conductivity of BeO ceramics using heavy ion irradiation and post-radiation annealing

Abstract The paper presents the results of research on changes in structural properties of BeO ceramics under heavy ion irradiation and post-radiation annealing. Irradiation was carried out on heavy ion accelerator DC-60 using Ni12+ ions with an energy of 100 MeV and irradiation fluence of 1013-1014 ions/cm2. According to X-ray diffraction analysis, it was found that a decrease of diffraction peaks intensity and their shift to small-angles region indicate an increase in interplanar distances and crystal lattice parameters, the change of which is caused by defects migration and their implantation into interstitial lattice site. For annealed samples an increased intensity of diffraction peaks, comparable in magnitude with original sample intensities, is observed. The increasing fluence of irradiation leads to a sharp decrease in crystallinity degree and the formation of more than 6.5% amorphous inclusions. Meanwhile, post-radiation annealing allows reducing amorphous inclusions concentration by 3%, which leads to a decrease in defects and vacancies in the structure. Reduction of deformations and amorphous inclusions as well as conservation of thermal conductivity coefficient indicate a potential applicability of post-radiation annealing of BeO ceramics as a method to control radiation defects accumulation and subsequent structure amorphization.

Characterization and Properties of High Amylose Mung Bean Starch Biodegradable Films Cross-linked with Malic Acid or Succinic Acid

Because of weak mechanical and highly hydrophilic properties of starch, various applications for starch have been limited. In this study, mung bean starch (MBS), one type of high amylose starch, was chosen for its potential film forming biopolymers. MBS films were prepared and modified by different types and contents of natural di-carboxylic acids, i.e. malic acid (MA) and succinic acid (SA) with different acidity and chemical structures. It was found from FTIR spectra that the extra peak position of 1700 cm−1 were observed, the evidence of ester group formation for MA- or SA- modified MBS films. The incorporation of MA or SA into MBS film also caused the decrease in degree of crystallinity, as confirmed by XRD technique. Additionally, the maximum strain at maximum load was highly improved with the addition of 30% MA or SA. Moreover, swelling power and water vapor permeability (WVP) of MBS film modified by SA were lower than those by MA. Morphology, biodegradability and thermal property of different acid-modified MBS films were also investigated.

The relevance of ultrafine fly ash properties and mechanical properties in its fly ash-cement gelation blocks via static pressure forming

Two fly ash samples, collected from the circulating fluidized bed (CFBFA) and pulverized boiler (PCFA) were ultrafine grinded and characterized by the scanning electron microscopy (SEM), the X-ray diffractometer (XRD) and the fourier transform infrared spectroscopy (FT-IR). The characterizations revealed the ultrafine grinding of fly ash resulted in not only the increase of their specific surface areas, also the decrease of crystallinity degree and the anion polymerization degree of silicates and aluminates. In comparison to CFBFA, PCFA showed a higher anion polymerization degree of silicates and aluminates. This was followed by strength behavior studies of the fly ash-cement gelation blocks. The mixing ratio of tested fly ash and cement was 1:1 (by wt%), and the fly ashes included those before and after ultrafine grinding. The results showed that ultrafine fly ash (UFFA)-cement blocks exhibited higher compressive strength as compared to that of original fly ash (OFA)-cement blocks, especially at their early stage. Compared with PCFA, CFBFA was more significant in improvement of mechanical properties of fly ash-cement block at its early age for the gelation block. Studies on the water absorption and the thermal weight loss revealed the effectiveness of UFFA in increasing the density and producing more C-S-H in order to improve the mechanical properties in gelation blocks. Due to the difference of CFBFA and PCFA in chemical and mineral compositions, the enhancement of CFBFA in producing C-S-H was greater at its early age but lower at its late age than those of PCFA.

Effect of mechanical mixing method of preparation of polyaniline-transition metal oxide composites on DC conductivity and humidity sensing response

In the present work, optimized polyaniline-titanium dioxide (PANI-TiO2) and polyaniline-yttrium oxide (PANI-Y2O3) composites were prepared by mechanical mixing of chemically synthesized PANI with TiO2 and Y2O3 transition metal oxides respectively. The Fourier transform infrared spectroscopy (FTIR) analysis confirmed relative decrease in depth of delocalization band of PANI in the composites as compared to that in PANI. The X-ray diffraction (XRD) studies confirmed decrease in degree of crystallinity and increase in inter-chain separation of PANI in the composites as compared to those of PANI. The scanning electron microscopy (SEM) images confirmed relatively more agglomerated and porous granular morphology of the composites as compared to that of PANI. Decrease in DC conductivity of the composites as compared to that of PANI confirmed experimentally and then supported theoretically by one dimensional variable ranging hopping (VRH) model. The PANI-TiO2 and PANI-Y2O3 composites, when studied for their humidity sensing performance, recorded remarkable maximum sensing response of 94 and 96% respectively at 97% RH as compared to 40% of PANI. The response and the recovery time of PANI-TiO2 composite were 95 and 122 s respectively and those of PANI-Y2O3 composite were 50 and 80 s respectively. Humidity sensing stability of the composites tested for a period of 1 month and confirmed.

Surface Modification of Nanoclay for the Synthesis of Polycaprolactone (PCL) – Clay Nanocomposite

This paper presents a new modification method to modify the surface of nanoclay (Na-MMT) to increase its d-spacing using Aminopropylisooctyl Polyhedral Oligomeric Silsesquioxane (AP-POSS) and the fabrication of Polycaprolactone (PCL) nanocomposite through solution intercalation technique. The structure and morphology of pure nanoclay, modified nanoclay (POSS-MMT) and the PCL nanocomposite were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Field Emission Scanning Electron Microscopy (FESEM). XRD revealed that the d-spacing of the POSS-MMT is increased by 0.64 nm as compared to pure nanoclay. FTIR and FESEM results also showed that AP-POSS were well dispersed and intercalated throughout the interlayer space of Na-MMT. An exfoliated structure was also observed for PCL/POSS-MMT nanocomposite. Thermal properties of the nanocomposite were investigated using Thermal Gravimetry Analysis (TGA) which recorded highest degradation temperature for PCL/POSS-MMT 1% nanocomposite which is 394.1°C at 50% weight loss (T50%) but a decrease in degradation temperature when POSS-MMT content is increased and Differential Scanning Calorimetry (DSC) analysis which showed highest melting and crystallization temperature for PCL/POSS-MMT 5% nanocomposite which is 56.6°C and 32.7°C respectively whereas a decrease in degree of crystallinity for PCL/POSS-MMT nanocomposite as compared to PCL/Na-MMT nanocomposite. This study affords an efficient modification method to obtain organoclay with larger interlayer d-spacing to enhance the properties of polymer nanocomposite.

Efficient hydrolysis of cellulose to glucose in water by agricultural residue-derived solid acid catalyst

A carbonaceous solid acid catalyst bearing weakly acidic carboxylic and phenolic functional groups was facilely prepared by the pyrolysis of cow dung followed by KOH activation. The prepared carbonaceous material showed low activity for the catalytic hydrolysis of raw cellulose in water (3.6% glucose yield). However, after the cellulose was pretreated by mixing with the carbonaceous catalyst in a ball mill, cellulose hydrolysis afforded a high glucose yield of 59.3% in water at 200 °C, and the glucose yield increased to 74% under the same reaction conditions in 0.015 wt% HCl aqueous solution. The increases were attributed to the decrease in degree of crystallinity of the cellulose, as well as good contact between the catalytic domain in the catalyst and the β-1,4-glycosidic bonds in the cellulose molecules by the mix-milling pretreatment. This work provides a promising strategy for efficient cellulose hydrolysis in water by a weakly acidic solid catalyst prepared from the agricultural residues.

Supramolecular formations and structural transformations in porous polyethersulfone/polyamide film materials

Structural properties of an ESPA-type polyethersulfone/polyamide film is studied by the method of X-ray diffractometry in the region of wide angles, and it is established that there is a slight decrease in the X-ray degree of crystallinity (DC) in the process of its water swelling. Data obtained by the method of smallangle X-ray scattering (SAXS) indicate that the sorption space of the amorphous phase of the ESPA film is formed, in fact, by three kinds of pores with different surface morphology. The pores of a smaller radius are capillaries with a smoother surface, and the large pores are channels with a “dissected” surface. Differential scanning calorimetry (DSC) studies reveal a bimodal endothermic peak at temperatures of 250 and 254°C, which is attributable to the melting of crystalline phases. A decrease in the degree of crystallinity upon the water sorption is associated with redistributing the proportion between structurally perfect crystalline phases with different melting enthalpy values in the crystallites of polyamide 6.6.

Influence of graphene oxide on photocatalytic enhancement of cerium dioxide

Graphene oxide (GO) was prepared by oxidizing purified natural flake graphite via modified Hummers method. The suspension of GO particles and cerium-based precursors were treated hydrothermally in order to prepare CeO2/GO composites. The disappearance of the [001] GO diffraction peak was observable in the XRD pattern for CeO2/GO composites because the crystal growth of CeO2 between the interlayer of GO destroyed the regular layer stacking of GO phase. However XPS spectra of O 1s core level and oxygen vacancies defect in CeO2 caused the decrease in degree of crystallinity. Composite of CeO2 with GO not only prevented the formation of extrinsic vacancies in the oxygen sub-lattice, but also prevented the switching from the major photoactive species Ce4+ to Ce3+.The photocatalytic activity measurements demonstrated that the CeO2/GO composites exhibited much higher photocatalytic activity than CeO2 for degradation of methylene blue (MB) under visible light irradiation. The enhancement of photocatalytic activity could be attributed to the excellently elevated absorption ability for the MB dye through π–π conjugation. As reported in PL results, the effective inhibition of the recombination of photogenerated electron–hole pairs due to the charge interaction between CeO2 and GO.