Surface modification of polystyrene with atomic oxygen radical anions-dissolved solution

A novel approach to the surface modification of medical poly(vinyl chloride) (PVC) with atomic oxygen radical anions‐dissolved solution (named as O– water) has been investigated. The O– water was generated by bubbling of the O– (atomic oxygen radical anion) flux into the deionized water. The surface hydrophilicities of the PVC films were investigated by contact angle measurements before and after the O– water treatment. Surface chemical compositions of the original and treated PVC films were studied using X‐ray photoelectron spectroscopy (XPS). The influence of the O– water on the surface roughness as well as morphological alterations of the PVC films was investigated by atomic force microscopy (AFM) measurements. Results show that the O– water treatment caused an obvious increase in the surface hydrophilicity and surface energy and also caused an alteration of the surface chemical composition, with an increase in surface roughness because of the etching effect. The modifications are attributed to the formation of oxygen‐containing functional groups (CO, CO, OCO, etc.) and dechlorination, mainly caused by the reactions between the molecules on PVC surfaces and the active oxygen species in the O– water. Present method, potentially, may be applied to the surface modification of polymers and other heat‐sensitive materials. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

PVDF blended PVDF-g-PMAA pH-responsive membrane: Effect of additives and solvents on membrane properties and performance

Atomic oxygen radical anion (O⋅-) represents an important type of reactive centre that exists in both chemical and biological systems. Gas-phase atomic clusters can be studied under isolated and well controlled conditions. Studies of O⋅--containing clusters in the gas-phase provide a unique strategy to interpret the chemistry of O⋅- radicals at a strictly molecular level. This review summarizes the research progresses made since 2013 for the reactivity of O⋅- radicals in the atomically precise metal oxide clusters including negatively charged, nanosized, and neutral heteronuclear metal clusters benefitting from the development of advanced experimental techniques. New electronic and geometric factors to control the reactivity and product selectivity of O⋅- radicals under dark and photo-irradiation conditions have been revealed. The detailed mechanisms of O⋅- generation have been discussed for the reaction systems of nanosized and heteroatom-doped metal oxide clusters. The catalytic reactions mediated by the O⋅- radicals in metal clusters have also been successfully established and the microscopic mechanisms about the dynamic generation and depletion of O⋅- radicals have been clearly understood. The studies of O⋅- containing metal oxide clusters in the gas-phase provided new insights into the chemistry of reactive oxygen species in related condensed-phase systems.

IntroductionThe current research tested the assumption that the addition of nano-carbonated hydroxyapatite (nCHAp) to Mineral Trioxide Aggregate (MTA) Angelus would modify its physicochemical properties and alter compositional characteristics that were relevant to the development of bioactive phases, without altering normal hydration dynamics.MethodsMTA angelus was blended with 5 wt% nano-CHAp and subjected to controlled hydration. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) was conducted to identify functional groups and affirm the inclusion of carbonate and phosphate ions. Phase composition was analyzed using X-ray diffraction (XRD). Surface morphology and elemental composition were analyzed by using Field Emission Scanning Electron Microscopy (FESEM) in conjunction with Energy Dispersive X-ray Spectroscopy (EDX). Porosity and microstructural integrity were also examined.ResultsATR-FTIR spectra showed peaks corresponding to characteristic functional groups of carbonates (CO32-) and phosphate (PO43-), affirming the incorporation of nano-CHAp chemically. XRD patterns affirmed the preservation of key hydration phases such as portlandite, tricalcium silicate, calcite, and bismuth oxide, with new calcium phosphate phases due to inclusion of nano-CHAp. FESEM images showed more dense microstructure with reduced porosity and reformed particle packing. EDX analysis showed the inclusion of phosphorus and notable increases in calcium and carbon content, corresponding with nano-CHAp inclusion. The modified MTA angelus preserves primary hydration pathways while having enhanced biofunctional availability of ions and surface morphology.ConclusionIntroduction of nano carbonated hydroxyapatite (nCHAp) brought about discernible changes in the composition of the cement matrix through the phase specific characteristics of XRD, ATR-FTIR, and energy-dispersive X-ray spectroscopy (EDS). These structural changes may create compositional environments that would support the development of mineral-related phases, but it would require further, more specific studies than the current one to confirm biological or clinical outcomes.

UAtomic oxygen radical anion (O−) is one of the most activeoxygen species, and has extremely high oxidation ability towardsmall-molecules of hydrocarbons. However, to our knowledge, littleis known about the effects of O− on cells of micro-organisms.This work showed that O− could quickly react with the Bacillussubtilis cells and seriously damage the cell walls a s well as theirother contents, leading to a fast and irreversible inactivation. SEM micrographs revealed that the cell structures were dramatically destroyed by their exposure to O−. The inactivation efficiencies of B. subtilis depend on the O−intensity, the initial population of cells and the treatmenttemperature, but not on the pH in the range of our investigation.For a cell concentration of 106 cfu/ml, the number of survivedcells dropped from 106 cfu/ml to 103 cfu/ml after aboutfive-minute irradiation by an O− flux in an intensity of 233nA/cm2 under a dry argon environment (30 oC, 1 atm,exposed size: 1.8 cm2). The inactivation mechanism ofmicro-organisms induced by O− is also discussed.

Surface modification and characterization of impregnated paper

One of the most efficient and cost-effective technologies for removing dye pollutants from industrial effluents is membrane separation. This study aims to investigate the effect of modified nanocomposite polyphenylsulfone (PPSU) membrane for removing Direct Orange102 (DO) dye from aqueous solutions. For this purpose, the PPSU membrane was surface modified by polydopamine (PPSU/PD) to improve its hydrophilic properties and separation performance. Then, a nanocomposite membrane, PPSU/PD/TiO2, was prepared by coating the surface of PPSU/PD with different dosages of TiO2 nanoparticles. The prepared PPSU/PD and PPSU/PD/TiO2 samples were characterized by employing attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and contact angle measurements. The ATR-FTIR analysis and FESEM images indicated that polydopamine and TiO2 were successfully coated on the surface of the membranes. Also, the results showed an increment in the hydrophilicity and roughness of the membrane after the addition of TiO2 nanoparticles. The performances of the fabricated membranes were compared in the separation of DO dye, Na2SO4, and bovine serum albumin (BSA). The best flux and rejection were obtained at 2 mg/ml of dopamine and 0.03 wt% of TiO2 loading. The prepared PPSU/PD/TiO2 membrane with high water flux provided impressive salt and dye removal. The results revealed that dye rejection increased from 80.5% for the PPSU membrane to 90% for the PPSU/PD membrane with a flux of 36 Lm−2h−1. For the PPSU/PD/TiO2 membrane, dye rejection and flux improved to 96.8% and 82 Lm−2h−1, respectively. The incorporation of TiO2 nanoparticles and polydopamine on the PPSU membrane surface enhanced the flux recovery ratio (FRR%) from 60.2% to 87%. The results of this study confirmed that modification of PPSU membrane by polydopamine and TiO2 nanoparticles leads to the improvement of the antifouling behavior and separation performance of the fabricated membrane toward the DO dye removal from aqueous solutions.

Vanadium oxide cluster anions (V2O5)nVxOy- (n = 1-31; x = 0, 1; and x + y ≤ 5) with different oxygen deficiencies (Δ = 2y-1-5x = 0, ± 1, and ±2) have been prepared by laser ablation and reacted to abstract hydrogen atoms from alkane molecules (n-butane) in a fast flow reactor. When the cluster size n is less than 25, the Δ = 1 series [(V2O5)nO- clusters] that can contain atomic oxygen radical anions (O•-) generally have much higher reactivity than the other four cluster series (Δ = -2, -1, 0, and 2), indicating that each atom counts in the hydrogen-atom abstraction (HAA) reactivity. Unexpectedly, all of the five cluster series have similar HAA reactivity when the cluster size is greater than 25. The critical dimension of vanadia particles separating the cluster behavior (each atom counts) from the bulk behavior (each atom contributes a little part) is thus about 1.6 nm (∼V50O125). The strong electron-phonon coupling of the vanadia particles has been proposed to create the O•- radicals (V5+ = O2-+ heat → V4+-O•-) for the n > 25 clusters with Δ = -2, -1, 0, and 2. Such a mechanism is supported by a comparative study with the scandium system [(Sc2O3)nScxOy- (n = 1-29; x = 0, 1; and x + y ≤ 4)] for which the Δ = 1 series [(Sc2O3)nO- clusters] always have much higher HAA reactivity than the other cluster series.

Novel short Agave americana based biocomposite and nanobiocomposites for automotive applications

The effects of physical properties and molecular structure of 200 nm polystyrene nanospheres (PSN) coated on silicon wafer exposed with daily solar flux were explored by field emission scanning electron microscope (FE-SEM) and attenuated total reflectance-Fourier transform infrared (ATR-FT-IR) spectrometer. It is revealed that the particles shape of PSN changed from spheric to eight-shaped after solar radiation. Reduction of the size as much as 29.5% after 5 minutes exposure was also observed in PSN particles. Changes in the molecular structure of the PSN particles after solar radiation were observed where some of the phenyl moieties of polystyrene broke down to facilitate carbon-carbon cross linkage bonds. These results demonstrated that the shrinkage of PSN particles is caused by the change of the molecular structure of polystyrene.

In this work, a series of Y-doped BiOBr photocatalysts with different yttrium contents were successfully synthesized through a facile ethylene glycol-assisted chemical precipitation method for the first time. The as-synthesized photocatalysts were characterized using N2 physical adsorption, X-ray diffraction, transmission electron microscope, field emission scanning electron microscope accompanied with an energy-dispersive X-ray spectroscopy (FESEM/EDS), attenuated total reflectance-Fourier transform infrared (ATR-FTIR), photoluminescence (PL) and UV–Vis diffuse reflectance spectra (UV–Vis/DRS). Doping of Y3+ ion had no obvious effect on the structure and morphology of BiOBr, however the BET surface area was greatly improved. The photocatalytic degradation of ciprofloxacin under indoor fluorescent light illumination showed that doping of Y3+ ion could bring about a significant increase in the photocatalytic activity. Among the doped samples, the 3%Y–BiOBr showed the highest photocatalytic activity for 20 ppm ciprofloxacin with degradation efficiency of 87.6% in just 60 min as compared to pristine BiOBr which had the degradation efficiency of 71.7%. Such enhanced photocatalytic activity could be attributed to the efficient separation of photogenerated electron–hole pairs, increased optical absorption and high surface area. A possible mechanism for the photocatalytic reaction has been proposed.

Facile fabrication of superhydrophobic steel surfaces with self-cleaning ability using nickel myristate/PDMS bilayer coating

Cellulose nanocrystals are an important class of bio‐based crystalline nanostructures, finding application in several technological fields, including paper and textile coating, biocomposite engineering, biocatalysts immobilization, etc. This study explores enzymatic hydrolysis of Avicel, using endoglucanase from Aspergillus niger , to find an environmentally friendly method to extract cellulose nanocrystals from cellulose sources. Enzymatic hydrolysis has the advantage of reduced energy consumption and higher environmental friendliness compared to acid hydrolysis. In this work, we report for the first time very high nanocrystals yield by combining mechanical pretreatment of the cellulose starting material with a ball miller and endoglucanase hydrolysis, as a result of an extensive optimization of reaction conditions. In particular, a ball milling pretreatment carried out for 50 minutes at 3 Hz, allowed to isolate enzymatic CNCs with 76 % yield and with crystallinity as high as 75 %. The materials were characterized by X‐Ray diffractometry, attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy, dynamic light scattering, zeta potential and field emission scanning electron microscopy (FE‐SEM). Their characteristics were compared with the properties of sulfated CNCs, prepared from Avicel by sulfuric acid hydrolysis. Our results are technologically relevant, as they contribute to the accessibility and sustainability of CNCs for a wide range of applications in various industries.

The present study aims to investigate the tribological performance of 2D nanoparticles such as graphene (G), molybdenum disulfide (MoS2), hexagonal boron nitride (hBN), and reduced graphene oxide (rGO) as gear lubricant additives. A new method of additive doping in gear lubricants was proposed and examined in terms of the degradation of lubricants. The additives were energized by ultrasonication, thermal agitation, and mechanical shearing to enhance the dispersibility and stability, which were confirmed using visual and rheological analysis. Further, the tribological performance of the nano-additives was studied by doping them in fresh lubricants, chemically degraded lubricants, and chemically degraded lubricants with surfactants. The results indicate that surface roughness and the method of mixing play a crucial role in reducing wear. The nano-additives exhibit an inverse relationship with the roughness, and their agglomeration results in a decline in performance. To mitigate agglomeration, oleic acid surfactant was employed, which diminished the effects of nano-additives and degraded the lubricant. The attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analysis revealed that the oleic acid and deteriorating reagent work synergistically, leading to enhanced wear volume and reduced friction. The nano-additives were characterized using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Overall, the study presents a comprehensive plan for new method of additive mixing, stability, dispersibility and tribological performance of the selected 2D nanoparticles.

Maltodextrin- and β-cyclodextrin-functionalized magnetic graphene oxide (mGO/β-CD/MD), a novel hydrophilic-lipophilic composite, was successfully fabricated and used for the co-extraction of triazines and triazoles from vegetable samples before HPLC-UV analysis. mGO/β-CD/MD was synthesized by chemical bonding of β-CD and MD to the surface of mGO, using epichlorohydrin (ECH) as a linker. The successful synthesis of mGO/β-CD/MD was confirmed by characterization tests, including attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET), and Barrett-Joyner-Halenda (BJH) analyses. The hydrophobic cavity of β-CD and a large number of hydroxyl groups on the MD structure contributed to the co-extraction of mentioned pesticides with a wide range of polarity. Under the optimized condition (sorbent amount, 30mg; desorption time, 10min; desorption solvent volume, 300 μL; desorption solvent, methanol/acetonitrile (1:1) containing 5% (v/v) acetic acid; extraction time, 20min; and pH of sample solution, 7.0), good linearity within the range 1.0-1000μg L-1 (r2 ≥ 0.992) was achieved. Extraction efficiencies were in the range 66.4-95.3%, and the limits of detection were 0.01-0.08μg L-1. Relative recoveries for spiked samples were obtained in the range 88.4-112.0%, indicating that the matrix effect was insignificant, and good precisions (intra- and inter-day) were also achieved (RSDs < 9.0%, n = 3). The results confirmed that the developed method was efficient for thedetermination oftrace amounts of pesticides in potato, tomato, and corn samples.