State-of-the-art technology: Recent investigations on laser-mediated synthesis of nanocomposites for environmental remediation

In both developing and industrialized/developed countries, various hazardous/toxic environmental pollutants are entering water bodies from organic and inorganic compounds (heavy metals and specifically dyes). The global population is growing whereas the accessibility of clean, potable and safe drinking water is decreasing, leading to world deterioration in human health and limitation of agricultural and/or economic development. Treatment of water/wastewater (mainly industrial water) via catalytic reduction/degradation of environmental pollutants is extremely critical and is a major concern/issue for public health. Light and/or laser ablation induced photocatalytic processes have attracted much attention during recent years for water treatment due to their good (photo)catalytic efficiencies in the reduction/degradation of organic/inorganic pollutants. Pulsed laser ablation (PLA) is a rather novel catalyst fabrication approach for the generation of nanostructures with special morphologies (nanoparticles (NPs), nanocrystals, nanocomposites, nanowires, etc.) and different compositions (metals, alloys, oxides, core-shell, etc.). Laser ablation in liquid (LAL) is generally considered a quickly growing approach for the synthesis and modification of nanomaterials for practical applications in diverse fields. LAL-synthesized nanomaterials have been identified as attractive nanocatalysts or valuable photocatalysts in (photo)catalytic reduction/degradation reactions. In this review, the laser ablation/irradiation strategies based on LAL are systematically described and the applications of LAL synthesized metal/metal oxide nanocatalysts with highly controlled nanostructures in the degradation/reduction of organic/inorganic water pollutants are highlighted along with their degradation/reduction mechanisms.     

Aging effect of atmospheric pressure plasma jet treated polycaprolactone polymer solutions on electrospinning properties

In previous work, an atmospheric pressure plasma jet was applied to successfully improve the electrospinnability of poly-ε-caprolactone (PCL) which enabled the fabrication of beadless nanofibers. In this paper, we report the aging effect of the plasma treatment to evaluate the robustness of the developed process. For this purpose, plasma-treated PCL polymer solutions with different exposure time were stored for 1 and 8 days and the aged solutions were analyzed in terms of conductivity, viscosity, surface tension, pH, and polymer molecular weight. During storage, the surface tension and acidity of the plasma-treated solutions were maintained constant. However, the viscosity was found to be significantly lower after 8 days which was attributed to PCL degradation. Electrospinning of all stored PCL solutions resulted in the generation of beadless PCL nanofibers. The plasma treatment effects were thus found to be highly stable over time and capable of producing high-quality PCL nanofibers up to 8 days. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48914.     

Microstructure and mechanical properties of a copper–stainless-steel dual-phase system prepared by spark plasma sintering

Spark plasma sintering (SPS) has been used to synthesise samples of a model dual-phase (DP) system, consisting of copper and AISI420 martensitic steel. Mixed powders were sintered at different temperatures in the range from 850°C to 1000°C using a loading pressure of 60?MPa. Tensile testing revealed dimpled fracture surfaces in samples sintered at higher temperatures, indicating ductile failure and good interfacial bonding between the phases, with the best results overall obtained for samples sintered from wet-mixed powders. The results show that by control of the mixing, sintering and post-sintering heat treatment conditions, the fabrication of dense samples covering a range of DP microstructures is possible using SPS, with independent control of the microstructure and properties of the two phases.     

Effects of GPTMS concentration and powder to liquid ratio on the flowability and biodegradation behaviors of 45S5 bioglass/tragacanth bioactive composite pastes

Injectable composite pastes were prepared using melt-derived 45S5 bioactive glass and tragacanth crosslinked by (3-glycidyloxypropyl)trimethoxysilane (GPTMS). The effect of powder to liquid ratio (P:L = 1.0:2.0–1.0:2.5) and GPTMS/tragacanth ratio (0.0–1.5) on the injectability, swelling behavior, rheology, bioactivity, and cellular behavior of the pastes was investigated. Based on the results, the apparent stability and consistency of the pastes increased upon crosslinking by GPTMS. Due to the increased interactions between tragacanth and glass, a hysteresis loop with larger area was formed in the presence of GPTMS. With increase of GPTMS:tragacanth ratio from 0 to 1.5, the swelling percent dropped from 24.65 to 16.25% after 24 h and the degradation percent also went down from 27.89 to 9.11% after 21 days in the simulated body fluid. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed a drop in the optical density of MG63 osteoblasts up to 30.07% after exposure to the GPTMS-crosslinked composite pastes for 3 days. However, the number of viable cells gradually increased in the presence of the pastes and the cell morphology remained unchanged over time. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47604.     

Enhanced photoelectrochemical water splitting in hierarchical porous ZnO/Reduced graphene oxide nanocomposite synthesized by sol-gel method

Today the utilization of solar energy to split water and its conversion to hydrogen and oxygen has been considered as a powerful way to solve the environmental crisis. Hierarchical porous nanostructured ZnO and ZnO/reduced graphene oxide (rGO) composite photoanodes are synthesized by innovated sol-gel method using triethylenetetramine (TETA) as a stabilizer. The hierarchical porous ZnO structure containing large agglomerates each consisting of tiny nanoparticles are formed. The X-ray diffraction analysis and Raman spectroscopy confirm the in-situ reduction of graphene oxide sheets during synthesis and formation of ZnO/rGO nanocomposite. Although the band gap and transmittance of the porous nanocomposites do not dramatically change by rGO addition, the main photoluminescence peak quenches entirely showing prolonging exciton lifetime. The ZnO/rGO porous structure achieved remarkably improved current density (1.02 mA cm^?2 at 1.5 V vs. Ag/AgCl) in 1 wt% rGO, up to 12 times higher compared to the bare ZnO (0.09 mA cm^?2 at 1.5 V vs. Ag/AgCl), which attributes to positive role of ZnO hierarchical porous structure and rGO electron separation/transportation. These findings provide new insights into the broad applicability of this methodology for promising future semiconductor/graphene composite in the field of photoelectrochemical water splitting.     

Remineralization effects of self-assembling peptide P11-4 associated with three materials on early enamel carious lesions: An in vitro study

The aim of this study was to assess the remineralization of enamel caries lesions using the self-assembling peptide P₁₁-4 associated with different materials. Artificial early enamel lesions were prepared on 154 primary teeth. The samples were randomly divided into eight groups: (1) control, (2) P₁₁-4, (3) fluoridate toothpaste (FT), (4) P₁₁-4 + FT, (5) casein phosphopeptide–amorphous calcium phosphate (CPP–ACP), (6) P₁₁-4 + CPP–ACP, (7) fluoridate bioactive glass toothpaste (BT), and (8) P₁₁-4 + BT. The surface enamel microhardness (EMH) and energy-dispersive X-ray spectroscopy (EDS) of the teeth were then measured at the baseline, after demineralization, and after 28 days of remineralization. The enamel surfaces were assessed by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The data were analyzed with one-way analysis of variance (ANOVA) (p < .05). EMH after demineralization was significantly lower than the baseline value (p < .001). The interventions led to an enhanced percentage of EMH recovery (%REMH), which was higher in Groups 6 and 7. There was no significant difference between Groups 3 and 4. Groups 1 and 2 had the lowest %REMH. The mean calcium/phosphate weight percentage ratio of P₁₁-4 was significantly lower than the others (p < .001). The FESEM and AFM images revealed mineral deposition on the eroded enamel and reductions in surface roughness in Groups 5 and 7.     

Earthquake-induced landslide mapping in the western Himalayas using medium resolution ASTER imagery

On 8 October 2005, a devastating earthquake struck northern Pakistan and several parts of Pakistani- and Indian-controlled Kashmir. The severely hit areas lie in close proximity to the most tectonically active region of the western Himalayas. The earthquake destroyed close to 400 000 houses and over 75 000 people lost their lives. The intensity of the earthquake was such that it triggered widespread landslides, which caused considerable destruction of the area's forests, and blocked the mountain roads and rivers. Satellite imagery-based analysis can be effectively used to provide critical geologic information for determining the causes of earthquakes, mapping of faults and lineaments, as well as for hazards and damage assessment mapping. In this study, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery acquired on 27 October 2005 was analysed to assess earthquake-induced land cover changes in severely hit areas. Image analysis techniques including intensity hue and saturation (IHS), principal component analysis (PCA), Normalized Difference Vegetation Index (NDVI) and Iterative Self-Organizing Data Analysis Technique (ISODATA) were applied on VNIR–SWIR bands of ASTER for the purpose of identification and mapping of landslides triggered by the earthquake in areas of northern Pakistan and Pakistani-controlled Kashmir. The techniques proved effective in identifying freshly exposed surfaces on mountain slopes, landslide scars and debris deposits. Accurate identification and mapping of landslides and slope failures can play an important role in post-earthquake damage assessment and hazards mapping in earthquake-prone mountainous areas.     

Sulfonated Beet Pulp as Solid Catalyst in One-Step Esterification of Industrial Palm Fatty Acid Distillate

In this research a new heterogeneous catalyst has been prepared for biodiesel production. The catalyst was prepared by sulfonating industrial sugar waste. Unlike homogeneous catalysts, which require further purification and separation from the biodiesel production reaction media, this inexpensive synthetic catalyst does not need to go through an additional separation process. This advantage consequently minimizes the total application costs. The catalyst was prepared by partially carbonizing sugar beet pulp at 400 °C. The carbonization product was then sulfonated with concentrated H₂SO₄ vapor in order to produce a solid catalyst. The prepared catalyst was used in the esterification reaction between palm fatty acid distillate (PFAD) and methanol. The effects of the temperature, methanol/PFAD ratio, reaction time and catalyst dosage on the efficiency of the production were individually investigated. The optimum biodiesel production occurred at 85 °C, a reaction time of 300 min, catalyst dosage of 3 g and methanol/PFAD ratio of 5:1 (mol/mol), lowering the acid value from 198 to 13.1 (mg KOH/g oil) or the equivalent, with a fatty acid methyl ester yield of around 92 %. The results suggest that the synthesized inexpensive catalyst is useful for biodiesel production from PFAD.     

High-efficiency remediation of cadmium (Cd2+) from aqueous solution using poultry manure– and farmyard manure–derived biochars

Farmyard manure (FYM-BC) and poultry manure (PM-BC) derived biochars were applied as adsorbents to remove Cd²⁺ from water. Results indicated that PM-BC was a more efficient adsorbent than FYM-BC at all experimental conditions. Maximum Cd²⁺ adsorption was observed at pH 4, temperature 318 K and contact time 1 h, regardless of biochar type. The Langmuir model predicted maximum adsorption capacity of 90.09 mg g^?1 for PM-BC. The data fitting to pseudo-second-order model proposed chemisorption of Cd²⁺ onto biochars. Thermodynamics indicated that adsorption was spontaneous and endothermic. Post-adsorption analysis provided evidences of strong chemical interactions between biochars’ functional groups and Cd²⁺ ions.