X-ray Diffractometry Analysis Research Articles

Phytomediated-Assisted Preparation of Cerium Oxide Nanoparticles Using Plant Extracts and Assessment of Their Structural and Optical Properties.

Cerium oxide nanoparticles were obtained using aqueous extracts of Chelidonium majus and Viscum album. X-ray diffractometry analysis confirmed the crystalline structure of the synthesized cerium oxide nanoparticles calcined at 600 °C. Scanning electron microscopy, UV-Vis reflectance and Raman spectroscopy, XPS, and fluorescence studies were utilized to interpret the morphological and optical properties of these nanoparticles. The STEM images revealed the spherical shape of the nanoparticles and that they were predominantly uniform in size. The optical band gap of our cerium nanoparticles was determined to be 3.3 and 3.0 eV from reflectance measurements using the Tauc plots. The nanoparticle sizes evaluated from the Raman band at 464 cm-1 due to the F2g mode of the cubic fluorite structure of cerium oxide are close to those determined from the XRD and STEM data. The fluorescence results showed emission bands at 425, 446, 467, and 480 nm. The electronic absorption spectra have exhibited an absorption band around 325 nm. The antioxidant potential of the cerium oxide nanoparticles was estimated by DPPH scavenging assay.

Investigation of Novel Nano-carbide WC/CoCr Coatings Applied by HVAF

AbstractWear leads to high material and energy losses in various industries. The manufacturing of novel nano-carbide WC/CoCr powder feedstock materials promises a further increase in the performance of thermally sprayed wear protection coatings. A novel experimental powder and a commercial ultra-fine carbide WC/CoCr reference are thermally sprayed onto a 1.0038 substrate by High Velocity Air Fuel (HVAF) spraying. The specimens are metallographically prepared and analyzed by means of light microscopy (LM) and scanning electron microscopy (SEM). Vickers Hardness testing is conducted by micro-indentation, and the porosities are determined by optical image analysis. X-ray diffractometry (XRD) analysis is used to investigate the phase retention. Fine nanocrystalline WC structures are preserved in the dense coatings. A significant effect of powder type on the porosity of the coating was found. No systematic relationships could be identified between the coating structure and the two parameter settings. It was possible to influence decarburization via both the powder type and the selected parameters. The resulting experimental and commercial nanostructured WC/CoCr coatings exhibit high, narrow hardness values with medians of 1.400 < HV0.3 < 1.470. The novel nanostructured coating can contribute to reduced wear and therefore improve the efficient utilization of critical raw materials like tungsten.

Evaluation of Performances of Calcined Laterite and Oyster Shell Powder Based Blended Geopolymer Binders

This work consisted in characterizing of calcined laterite and oyster shell powder based blended geopolymer binders. To do this, raw laterite taken from Soa in the city of Yaoundé and oyster shells extracted from Mouanko in the Sanaga-Maritime were initially air-dried, then dried at 105 °C, before being calcined at 500 °C and 200 °C respectively for 2 hours. These samples were subjected to preliminary studies, i.e. determination of their chemical and mineralogical compositions, particle size distributions, densities, as well as thermal analysis for the synthesis of geopolymer binders. X-ray diffractometry, thermal and gravimetric analysis were carried out on the oyster shell powder and laterite, in order to elucidate the time and degree of calcination of the two samples, the evolution of the linear shrinkage, the setting time as well as the compressive and flexural strengths of the geopolymer binders. The results obtained show that oyster shells are rich in CaCO3 and contain crystalline phases, while laterite is rich in silica, iron (FeCO3) and alumina (Al2O3). The geopolymer samples: Lat + 0% oyster shells have a setting time between 125 and 168 min for a compressive strength of about 47 MPa. The peak strength is observed around 15% addition of oyster shell powder, i.e. 53.5 MPa at 28 days with an increased setting time. This strength was decreased from 25 % of addition of oyster shells, despite the increase observed in the setting time. It appears from this study that the addition of 15% oyster shell increases the compressive strength of the geopolymer, but also leads to a considerable decrease in absorption rate. Above this rate, the compressive strength decreases drastically and concomitantly the setting time increases.

Adsorption of PO43-, Cd(II), Pb(II), Cu(II), As(III), and As(V) using a carbonised Mn-based metal–organic framework

Metal–organic frameworks (MOFs) are adsorbents suitable for water treatment. However, they are often water soluble and poorly processible, limiting their industrial applications. This study aims to develop a carbonized MOFs with high adsorption performance based on MOFs. Here, we report the production of Mn-MOF [Mn(DMF)2(H2DHTPA)]n (where DMF is N,N-dimethylformamide and H4DHTPA is 2,5-dihydroxyterephthalic acid) via a solvothermal method. This MOF shows good adsorption performance for various ions but dissolves easily in water. However, Mn-MOF-500 which was obtained by carbonising Mn-MOF at 500 °C shows high water stability. Thus, the adsorption properties of Mn-MOF-500 were investigated, revealing adsorption capacities for PO43-, Cd(II), Pb(II), Cu(II), As(III), and As(V) of 126.66, 88.46, 356.21, 146.92, 51.28, and 166.10 mg/g, respectively. Based on the adsorption isotherms and the adsorption kinetics, the adsorption of PO43-, Cd(II), and As(III) occurs via monolayer chemisorption, whereas that of Pb(II), Cu(II), and As(V) occurs via monolayer chemisorption and physisorption in pores. X-ray diffractometry and X-ray photoelectron spectroscopy analysis showed that P, Cd(II), Pb(II), Cu(II), As(III), and As(V) were adsorbed on Mn-MOF-500 as PO43-, Cd(OH)2, PbO and Pb(OH)2, Cu(OH)2, Mn3(AsO3)2, and MnHAsO4, respectively.

Manufacturing and characterization of a 3D printed lithium disilicate ceramic via robocasting: A pilot study

ObjectiveThe objective of this study was to manufacture and to evaluate the physico-mechanical properties of the Lithium disilicate (Li2O5Si2) ceramic structures fabricated using additive manufacturing (3D printing). MethodsLi2O5Si2 samples were divided into (n = 30/group): SM (subtractively manufactured) and AR (additive/robocasting). For the AR group, Li2O5Si2 powder was combined with ammonium polyacrylate, hydroxypropyl methylcellulose, and polyelectrolyte to create a colloidal gel, which was then used for printing. A digital CAD model of a disc was designed, and the G-code transferred to a custom built DIW 3D printer. The control group samples were prepared using pre-crystallized ceramic blocks, which were cut to obtain discs with same dimensions as the AR group. Disc-shaped specimens from both groups were crystallized at 840 °C. Mechanical properties were evaluated using biaxial flexural strength test (BFS) and Vickers hardness test. Representative fractographic images of the specimens were acquired using scanning electron microscopy (SEM) to analyze the fracture origin and crack propagation. Energy-dispersive X-ray spectroscopy (EDS) and attenuated total reflection Fourier transform infrared spectroscopy (FTIR-ATR) were used for chemical analysis, and X-ray diffractometry (XRD) was performed to analyze the crystalline phases. ResultsAR group yielded lower values of BFS (120.02 MPa ±33.91) and hardness (4.07 GPa ±0.30), relative to the SM group, (325.09 MPa ±63.98) and (5.63 GPa ±0.14), respectively. For EDS analysis, AR and SM groups showed similar elemental composition. In FTIR-ATR analysis, higher peaks referring to the crystalline structure were found for SM group. XRD analysis indicated a decreased formation of Li2O5Si2 from Lithium metasilicate (Li2O–SiO2) in the AM group. SEM micrographs showed a more porous microstructure associated with the 3D printed samples. SignificanceThe viability of fabricating Li2O5Si2 ceramic constructs using the Robocasting technique was successful. However, the samples prepared using subtractive manufacturing presented higher mechanical properties compared to the 3D printed constructs. The difference in properties between the manufacturing may be correlated to the decreased formation of Li2O5Si2 crystals and higher degrees of porosity.

Comparative study of the photocatalytic degradation of tetracycline under visible light irradiation using Bi24O31Br11-anchored carbonaceous and silicates catalyst support

Abstract This study compared two hydrothermally synthesized heterojunctions composites, Bi24O31Br10 – carbonaceous (activated carbon from zinc chloride [ACZ], phosphoric acid [ACH], carbonized material [CM]), and Bi24O31Br10 – silicates (SBA-15 and MCM-41), with nanosheets structure. The photocatalytic degradation of tetracycline (TC) was used to evaluate the synergistic influence of the catalyst supports for the corresponding heterojunction composites. The X-Ray diffractometry (XRD), Fourier transform infrared spectroscopy and scanning electron microscopy (SEM) confirmed the synthesis of the Bi24O31Br10 (BOB) – composites. After 120 min of visible LED light photocatalytic reactions, the degradation trend in removal efficiency of TC was BOB-ACZ > BOB > ACH > BOB-CM > BOB-MCM-41 > BOB-SBA-15 > BOB. The study reveals that Bi24O31Br11 – carbonaceous composite exhibits much better degradation efficiency than Bi24O31Br11 – silicates. Crucially, the synergistic surface interaction of ACZ with BOB, and the efficient separation of photogenerated charge carriers, from the SEM, XRD analysis, and photocurrent response, confirmed the photocatalytic enhancement of the heterojunction formation of the BOB-ACZ composite. This study further provides convincing insights on the superiority of carbonaceous nanomaterial to silica materials as efficient catalyst support in catalytic applications.

Controlled release of a non-steroidal anti-inflammatory drug from a photocurable polymeric calcium phosphate cement

In this research, a photocurable composite based on tetracalcuim phosphate ceramic and, hydroxyethyl methacrylate-modified poly(acrylic-maleic acid) was developed and studied as a potential drug delivery system for bone defects. Different concentrations (5, 10 and 20 wt. %) of a non-steroidal anti-inflammatory drug, Indomethacin, were loaded on to the composite and its release behavior was investigated in phosphate buffered solution during 504 h. The obtained release data were fitted by both power law (Peppas) and Weibull equations. The composites were also characterized after different soaking periods using X-ray diffractometry (XRD), scanning electron microscopy (SEM) and Fourier transforming infrared spectroscopy. The results of XRD and SEM analyses revealed the formation of nanosized needle/flake-like apatite crystals on the composites surfaces; however, better apatite formation was observed for the composites loaded with higher amounts of Indomethacin. The morphological observations and quantitative estimations revealed that the loaded composites were gradually degraded in the phosphate-buffered saline. Moreover, a controlled release of Indomethacin was found from the composites in which a higher drug concentration led to a more drug level as well as sustained release profile. In drug release modeling, better regression coefficient was obtained from the Weibull equation, compared to the power law, meaning that the Weibull equation suggests a better description of the indomethacin release from the composites during the whole period of the test. In conclusion, the photocurable composite with apatite formation ability can be successfully used for the controlled release of indomethacin as an anti-inflammatory drug in bone defects.

Novel carbonation solidification process for recovery of Zn-contaminated slurry: Strength and leachability aspects

In this study, a continuous process of foam drying pre-treatment with steel slag powder and carbonation solidification (SSFD-C) was used to recycle zinc- (Zn-) contaminated slurry, which achieved the first implementation of accelerated carbonation technology in contaminated slurry recovery. Unlike conventional carbonation solidification methods, the steel slag component of the slurry also underwent a drying process as part of the SSFD-C process. During the drying process, the mechanism whereby the contaminating Zn ions interacted with steel slag, and the effects of these interactions on the carbonation efficiency and mechanical properties of the carbonated soil (CS) were investigated by testing CO2 uptake and unconfined compressive strength (UCS). In addition, the stabilizing effects of the drying and carbonation processes on Zn contamination were evaluated by establishing pH values and Zn leaching concentrations of the dried soil (DS) and CS under water/acid leaching. This study makes several important contributions to the existing literature on Zn contamination and its effect on the UCS of CS. We found that Zn contamination negatively impacted the UCS of CS by impairing its carbonation efficiency. Additionally, it was found that both drying and carbonation processes can efficiently reduce acid-leached Zn concentration by 45–85% compared to untreated contaminated samples. It was established that Zn contamination is stabilized as Zn(OH)2 in DS and CS specimens through an X-ray diffractometry and derivative thermogravimetric analysis. Furthermore, our study highlights the benefit of carbonation in stabilizing Zn leaching, as it lowers the pH value of water-leached samples.

Characteristics, Genesis, and Hydrocarbon Aspects of Lacustrine Siderite-Rich Marl (Early Jurassic): A Case Study in the Dachanggou Basin, Xinjiang, Northwest China

Thinly bedded marls are widely developed in the oil shale-bearing series of the Lower Jurassic Badaowan Formation in the Dachanggou Basin (Northwest China). In this study, the characteristics, genesis, and hydrocarbon prospects of marls in a lacustrine organic-rich shale series were analyzed via X-ray diffractometry, element geochemistry, carbon and oxygen isotope analysis, total organic carbon content analysis, rock pyrolysis, and sedimentary analysis. The results show that the main carbonate component of marl is siderite, which is mainly present in areas with lithologic changes at the top and bottom of organic shale, and that the development of a thick siderite-rich marl is closely related to the presence of the thick oil shale. The elemental indicators of the sedimentary environment show that the low initial organic matter abundance and low clastic input were conducive to the formation of siderite and that the water body in the marl development period provided an oxic–suboxic environment, although the formation of siderite was still disturbed by oxygen in the relatively reduced bottom sediments. The carbonate carbon isotopes in the marl are clearly positive, indicating that δ13C-rich carbonate provided by methanogens decomposing sedimentary organic matter contributed to the siderite formation. These siderite-rich marls formed in a relatively restricted environment; i.e., they were deposited close to a rich organic layer, with a sufficient methanogenic metabolite CO2 content and a small amount of terrigenous clastic input. These factors reached an appropriate balance, thus forming a narrow zone (partial shallow lake and delta front facies). Although the hydrocarbon generation potential of the marl is low relative to that of other source rocks, the thin marl that is widespread in continental shallow-water organic-rich sedimentary systems can improve the fracturing ability of shale reservoirs, which is of far-reaching significance for the development of shale oil and gas in continental shallow-water sedimentary systems.

Acid and Base modified Pectin from Orange Peel as an Effective Bio-adsorbent for Pb(II) and Cr(VI) from Textile Industry Wastewater

Modifying the methoxyl group on pectin from Siam orange peel (Citrus nobilis) has been done. Pectin was obtained from the peel of Siam orange by extraction method. The modified pectin obtained were analyzed using the FT-IR (Fourier Transform-Infra Red Spectroscopy) method, the XRD (X-Ray Diffractometry), and surface appearance images using SEM (Scanning Electron Microscopy). Pb(II) and Cr(VI) metals which can be adsorbed by the adsorbent then analyzed by UV-Visible Spectrophotometer. The results of the FT-IR analysis was found that the modification of the methoxyl group was successful. XRD analysis showed that the modified pectin adsorbent produced amorphous properties. The maximum pH for Pb(II) adsorption was obtained, namely pH = 6 and the maximum pH for Cr(VI) adsorption was pH =7. The best adsorption time variation for Pb(II) was 240 min and for Cr(VI) was 500 min. The best adsorbent for adsorption of Pb(II) was base-modified pectin adsorbent, while the best adsorbent for adsorption of Cr(VI) was base-modified pectin adsorbent. It could be proven that base-modified pectin was able to adsorb Pb(II) and acid-modified pectin was able to absorb Cr(VI) better (Pb(II) 80% adsorption percentage and 90% Cr(VI) adsorption percentage) than previous studies, namely pectin without modification (adsorption percentage obtained 60-70%).

An NIR-Driven Upconversion/C3N4/CoP Photocatalyst for Efficient Hydrogen Production by Inhibiting Electron-Hole Pair Recombination for Alzheimer's Disease Therapy.

Redox imbalance and abnormal amyloid protein (Aβ) buildup are key factors in the etiology of Alzheimer's disease (AD). As an antioxidant, the hydrogen molecule (H2) has the potential to cure AD by specifically scavenging highly harmful reactive oxygen species (ROS) such as •OH. However, due to the low solubility of H2 (1.6 ppm), the traditional H2 administration pathway cannot easily achieve long-term and effective accumulation of H2 in the foci. Therefore, how to achieve the continuous release of H2 in situ is the key to improve the therapeutic effect on AD. As a corollary, we designed a rare earth ion doped g-C3N4 upconversion photocatalyst, which can respond to NIR and realize the continuous production of H2 by photocatalytic decomposition of H2O in biological tissue, which avoids the problem of the poor penetration of visible light. The introduction of CoP cocatalyst accelerates the separation and transfer of photogenerated electrons in g-C3N4, thus improving the photocatalytic activity of hydrogen evolution reaction. The morphology of the composite photocatalyst was shown by transmission electron microscopy, and the crystal structure was studied by X-ray diffractometry and Raman analysis. In addition, the ability of g-C3N4 to chelate metal ions and the photothermal properties of CoP can inhibit Aβ and reduce the deposition of Aβ in the brain. Efficient in situ hydrogen production therapy combined with multitarget synergism solves the problem of a poor therapeutic effect of a single target. In vivo studies have shown that UCNP@CoP@g-C3N4 can reduce Aβ deposition, improve memory impairment, and reduce neuroinflammation in AD mice.

Phase Morphology, Mechanical, and Thermal Properties of Calcium Carbonate-Reinforced Poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) Bioplastics

Poly(L-lactide) (PLLA) is a promising candidate as a bioplastic because of its non-toxicity and biodegradability. However, the low flexibility of PLLA limits its use in many applications. Poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide) (PLLA-b-PEG-b-PLLA) block copolymer is of interest for bioplastic applications due to its superior flexibility compared to PLLA. The aim of this work is to modify PLLA-b-PEG-b-PLLA using a low-cost calcium carbonate (CaCO3) filler to improve material properties compared to PLLA/CaCO3 composites. The addition of CaCO3 enhanced the crystallinity and thermal stability for the PLLA-b-PEG-b-PLLA matrix but not for the PLLA matrix, as determined by differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and thermogravimetric analysis (TGA). Phase morphology investigation using scanning electron microscopy (SEM) revealed that the interfacial adhesion between PLLA-b-PEG-b-PLLA and CaCO3 was stronger than between PLLA and CaCO3. Additionally, tensile testing was carried out to determine the mechanical properties of the composites. With the addition of CaCO3, the tensile stress and Young's modulus of the PLLA-b-PEG-b-PLLA matrix were increased, whereas these properties of the PLLA matrix were significantly decreased. Thus, CaCO3 shows great promise as an inexpensive filler that can induce nucleation and reinforcing effects for PLLA-b-PEG-b-PLLA bioplastics.

Novel Method for the Production of Titanium Foams to Reduce Stress Shielding in Implants.

Titanium foams have potential applications in orthopedic and dental implants because of their low elastic modulus and good bone in-growth properties. In the present study, a novel method for the preparation of three-dimensional interconnected microporous titanium foams has been developed. This method is based on the insertion of a filler metal into the titanium metal by arc melting, followed by its removal by an electrochemical dealloying process for the development of foams. Complete removal of the filler metal by the electrochemical dealloying process was confirmed by an X-ray diffractometry (XRD) analysis, whereas scanning electron microscopy (SEM) analysis of the developed foams showed the development of interconnected porosity. Ti foams with different levels of porosities were successfully developed by varying the amount of the filler metal. Mechanical and thermal characterizations of the developed foams were carried out using compression testing and laser flash apparatus, respectively. The yield strength and elastic modulus of the developed foams were found to decrease by increasing the volume fraction of pores. The elastic modulus of the developed titanium foams (15.5-36 GPa) was found to be closer to that of human bones, whereas their yield strength (147-170 MPa) remained higher than that of human bones. It is therefore believed that the developed Ti foams can help in reducing the problem of stress shielding observed in orthopedic implants. The thermal diffusivity of the developed foams (4.3-0.69 mm2/s) was found to be very close to that of human dentine.

Особенности изменения интенсивностей основных полос фотолюминесценции ионов Tb-=SUP=-3+-=/SUP=- и их сателлитов в поликристаллическом люминофоре Gd-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-:Tb(3 mol%)

Samples of Gd2O3:Tb(3 mol%) phosphor were obtained by sol-gel method followed by annealing at 800oC and 1200oC in air. At high annealing temperature, the intensities of the main emission bands 484 and 541 nm increase, but the ratio of the intensities of these emission bands to their satellites 493 and 549 nm respectively decreases. Based on the analysis of X-ray diffractometry, radiation spectra, far-infrared and Raman spectroscopy, as well as diffuse reflectance spectroscopy, we established: the increase in the crystallinity of the samples with a significant reduction of the lattice strain stress at elevated annealing temperatures, changes in the structure of the bandgap with degenerated acceptor and donor zones of impurities Tb4+ and Tb3+ respectively. The diffuse reflection spectra of the sample after annealing at 800oC under optical excitation showed a direct charge transition through the bandgap with Eg = 2.56 eV. After elevated annealing temperature the concentration of Tb4+ ions decreases due to reduction to Tb3+. As a result, at low excitation energies the degeneracy of the acceptor zone is still preserved and there is a direct transition of charges through the bandgap with Eg = 2.55 eV. At high excitation energies the degeneracy of the acceptor zone is removed and there is a direct transition through the bandgap with Eg = 3.39 eV. These effects are accompanied by a relatively large increase in the emission intensity of the satellites, especially at the 549 nm.

Peculiarities of changes in the intensities of the main photoluminescence bands of Tb-=SUP=-3+-=/SUP=- ions and their satellites in polycrystalline Gd-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=- : Tb(3 mol%)

Samples of Gd2O3 : Tb(3 mol%) phosphor were obtained by sol-gel method followed by annealing at 800oC and 1200oC in air. At high annealing temperature, the intensities of the main emission bands 484 and 541 nm increase, but the ratio of the intensities of these emission bands to their satellites 493 and 549 nm respectively decreases. Based on the analysis of X-ray diffractometry, emission spectra, far-infrared and Raman spectroscopy, as well as diffuse reflectance spectroscopy, we established: the increase in the crystallinity of the samples with a significant reduction of the lattice strain stress at elevated annealing temperatures, changes in the structure of the bandgap with degenerated acceptor and donor zones of impurities Tb4+ and Tb3+ respectively. The diffuse reflection spectra of the sample after annealing at 800oC under optical excitation showed a direct charge transition through the bandgap with Eg=2.56 eV. After elevated annealing temperature the concentration of Tb4+ ions decreases due to reduction to Tb3+. As a result, at low excitation energies the degeneracy of the acceptor zone is still preserved and there is a direct transition of charges through the bandgap with Eg=2.55 eV. At high excitation energies the degeneracy of the acceptor zone is removed and there is a direct transition through the bandgap with Eg=3.39 eV. These effects are accompanied by a relatively large increase in the emission intensity of the satellites, especially at the 549 nm. Keywords: Gd oxide, Tb3++ photoluminescence spectra, far infrared and Raman spectroscopy spectra, structure of the bandgape, distribution of Tb3+ and Tb4+ in cation sublattice.

Immobilization of heavy metals in tannery sludge by the formation of tobermorite in subcritical water treatment with rice husk silica.

Tannery sludge, heavy metals (HMs) enriched hazardous solid waste, is produced extensively in many regions of the world. Even though the sludge is hazardous, it can be considered a material resource, if organic matter and HMs in the sludge can be stabilized to minimize its negative environmental impacts. This research aimed to evaluate the efficacy of using subcritical water (SCW) treatment for tannery sludge treatment through immobilization and thus reduction of HMs to mitigate their potential environmental risk and toxicity. HMs in the tannery sludge were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) and the average concentration of HMs (mg kg-1) was found in the following decreasing order of Cr (12 950) > Fe (1265) > Cu (76) > Mn (44) > Zn (36) > Pb (14) with very high Cr concentration. The result of toxicity characteristics leaching procedure and sequential extraction procedure tests revealed that the raw tannery sludge leachate contained 11.24 mg L-1 Cr, which classified the raw tannery sludge into a very high-risk category. After SCW treatment, the concentration of Cr in leachate was reduced to 1.6 mg L-1 indicating risk reduction to a low-risk category. The eco-toxicity levels of other HMs also decreased considerably after SCW treatment. X-ray diffractometry (XRD) and scanning electron microscopy (SEM) analysis were employed to identify the effective immobilizing substances formed in the SCW treatment process. The favorable formation of immobilizing orthorhombic tobermorite (Ca5Si6O16(OH)2·4H2O) at 240 °C in the SCW treatment process was confirmed by XRD and SEM analysis. The results confirmed that the formation of 11 Å tobermorite is capable of strongly immobilizing HMs in the SCW treatment process. Further, both orthorhombic 11 Å tobermorite and 9 Å tobermorite were successfully synthesized by SCW treatment on a mixture of tannery sludge including rice husk silica and Ca(OH)2 with water under rather mild conditions. Hence, it can be concluded that SCW treatment of tannery sludge with supplementary silica from rice husk can effectively immobilize the HMs and significantly reduce their environmental risk through tobermorite formation.

PVP solid dispersions containing Poloxamer 407 or TPGS for the improvement of ursolic acid release

Solid dispersions (SDs) of ursolic acid (UA) were developed using polyvinylpyrrolidone K30 (PVP K30) in combination with non-ionic surfactants, such as D-α-tocopherol polyethylene glycol 1000 succinate (TPGS) or poloxamer 407 (P407) with the aim of enhancing solubility and in vitro release of the UA. SDs were investigated using a 24 full factorial design, subsequently the selected formulations were characterized for water solubility, X-ray diffractometry (XRD), differential scanning calorimetry (DSC), particle diameter, scanning electron microscopy, drug content, physical-chemical stability and in vitro release profile. SDs showed higher UA water-solubility than physical mixtures (PMs), which was attributed by transition of the drug from crystalline to amorphous or molecular state in the SDs, as indicated by XRD and DSC analyses. SD1 (with P407) and SD2 (with TPGS) were chosen for further investigation because they had higher drug load. SD1 proved to be more stable than SD2, revealing that P407 contributed to ensure the stability of the UA. Furthermore, SD1 and SD2 increased UA release by diffusion and swelling-controlled transport, following the Weibull model. Thus, solid dispersions obtained with PVP k-30 and P407 proved to be advantageous to enhance aqueous solubility and stability of UA.

Psidium guajava leaf extract mediated green synthesis of silver nanoparticles and its application in antibacterial coatings.

In this study, Psidium guajava (P. guajava) leaf extract-assisted silver nanoparticles (AgNPs) were synthesized and their antibacterial activities were investigated. The synthesized green AgNPs were characterized by various analytical techniques including UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) spectroscopy, etc. From the UV-Vis spectroscopic analysis, the formation of nanoparticles has been confirmed by the color change from light yellow to reddish brown of the solution due to the excitation of the surface plasmon resonance peak at 430 nm. In addition, the FTIR study showed the reduction of Ag ions owing to the presence of biomolecules in the leaf extract, which acted as reducing as well as capping agents. Furthermore, XRD analysis reveals the identified 2θ peaks of AgNPs at ∼39° with cubic structure. The FE-SEM micrograph illustrated the material was formed in nano-dimensions, with an average particle size of ∼12 nm and almost spherical in shape. Moreover, P. guajava-mediated AgNPs demonstrated good antibacterial activity against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacterial strains. The synthesis was performed by a bio-reduction process where a bioactive agent is responsible for reducing metallic ions to metallic nanoparticles as an eco-friendly, cost-effective, non-toxic, one-step, and sustainable method. Therefore, this study may create an imperative synthetic route for the fabrication of green-AgNPs and their application in antibacterial coatings in cotton textiles.

Surface functionalized silver-doped ZnO nanocatalyst: a sustainable cooperative catalytic, photocatalytic and antibacterial platform for waste treatment.

The different dyes used and discharged in industrial settings and microbial pathogenic issues have raised serious concerns about the content of bodies of water and the impact that dyes and microbes have on the environment and human health. Efficient treatment of contaminated water is thus a major challenge that is of great interest to researchers around the world. In the present work, we have fabricated functionalized silver-doped ZnO nanoparticles (Ag-doped ZnO NPs) via a hydrothermal method for wastewater treatment. X-ray photoelectron spectroscopy analysis confirmed the doping of Ag with ZnO NPs, and X-ray diffractometry analysis showed a decreasing trend in the crystallite size of the synthesized ZnO NPs with increased Ag concentration. Field emission scanning electron microscopy study of pure ZnO NPs and Ag-doped ZnO NPs revealed nanocrystal aggregates with mixed morphologies, such as hexagonal and rod-shaped structures. Distribution of Ag on the ZnO lattice is confirmed by high-resolution transmission electron microscopy analysis. ZnO NPs with 4 wt% Ag doping showed a maximum degradation of ∼95% in 1.5 h of malachite green dye (80 mg L-1) under visible light and ∼85% in 4 h under dark conditions. Up to five successive treatment cycles using the 4 wt% Ag-doped ZnO NP nanocatalyst confirmed its reusability, as it was still capable of degrading ∼86% and 82% of the dye under visible light and dark conditions, respectively. This limits the risk of nanotoxicity and aids the cost-effectiveness of the overall treatment process. The synthesized NPs showed antibacterial activity in a dose-dependent manner. The zone of inhibition of the Ag-doped ZnO NPs was higher than that of the pure ZnO NPs for all doping content. The studied Ag-doped ZnO NPs thus offer a significant eco-friendly route for the effective treatment of water contaminated with synthetic dyes and fecal bacterial load.

First record of plant macrofossil from the Boa Vista Formation, Takutu Basin, Roraima State, Brazil

Clayey intraclasts containing leaves preserved as impressions and compressions were collected from the Takutu River channel in the State of Roraima, Brazil. In the present study, 23 leaf fragments are described (morphologically and anatomically) and their taxonomic identity is proposed. These fossiliferous intraclasts were suggested in previous studies as coming from the Boa Vista Formation (Upper Pleistocene–Holocene). With the aim of finding new evidence to support this correlation, X-ray diffractometry (XRD) and Laser induced-breakdown spectroscopy (LIBS) analysis were performed, comparing the fossiliferous sample with two outcrops from the Boa Vista Formation. The results evidenced the chemical and mineralogical similarity between the fossiliferous intraclasts and both outcrops, suggesting their correlation with the Boa Vista Formation. Taxonomically, the specimens were recognized as fossil representatives of Dilleniaceae Salisb., Byrsonima Rich. ex Kunth (Malpighiaceae), Zanthoxylum L. (Rutaceae), and other six morphotypes. These taxa represent typical elements of the savanna (lavrados) of Roraima. The anatomical-cutillary characters of the mummified leaves indicate the dominance of xeromorphic plants, similar to the predominant woody species in the “lavrado” today, thus suggesting the same climatic-environmental conditions. Keywords: fossil leaves, leaf architecture, cuticular anatomy, angiosperm, Cenozoic.