A comparative study of physical properties in Fe3O4 nanoparticles prepared by coprecipitation and citrate methods

Magnetite exhibits unique structural, electronic, and magnetic properties in extreme conditions that are of great research interest. In this work, the effects of preparation technique on X‐ray peak broadening, magnetic and elastic moduli properties of Fe₃O₄ nanoparticles prepared by coprecipitation (FcP‐NPs) and citrate (FC‐NPs) methods have been investigated. The structural characterization of the samples is evidence for a cubic structure with Fd‐3m space group. The Williamson‐Hall analysis was used to study crystallite sizes and lattice strain of the samples and also stress and energy density. In addition, the crystallite sizes are compared with the particle sizes and the magnetic core sizes obtained from TEM and VSM methods, respectively. In addition, the cation distribution obtained from calculated inversion parameter indicate that in the smaller particles, more amount of Fe²⁺ on the tetrahedral sites can be related to higher stress induced in the FcP‐NPs compared to the FC‐NPs. The saturation magnetization of the FcP‐NPs is almost two times bigger than the saturation magnetization of the FC‐NPs. It could be attributed to the decrease in the negative interaction on the octahedral site and also the magnetic moment on the tetrahedral site of the FcP‐NPs. The increase in force constants of the FC‐NPs determined by infrared spectra analysis compared to FcP‐NPs suggests the strengthening of their interatomic bonding. The values of shear and longitudinal wave velocities obtained from force constants have been used to determine the values of Young's modulus, rigidity modulus, bulk modulus, and Debye temperature. By comparison of the elastic results of FC‐NPs with the FcP‐NPs, we can observe that the elastic properties of the F‐NPs have been improved by synthesis method, while Poisson's ratio almost remains constant. In addition, using the values of the compliance s_ij obtained from elastic stiffness constants, the values of Young's modulus and Poisson's ratio along the oriented direction [hkl] have been calculated for the samples.     

Chitosan/MCM‐41 nanocomposites for efficient beryllium separation

Chitosan nanoparticles (Ch NPs) with individual particles 10–30 nm in size and average aggregate sizes of 240 nm were prepared via ionic gelation. Ordered mesoporous Mobil Composition of Matter No. 41 (MCM‐41) with a surface area of 1590 m²/g was prepared via a sol–gel method. The nanocomposites were prepared via the in situ dispersion of MCM‐41 in chitosan followed by ionic gelation with a multivalent anion to produce MCM‐41‐impregnated Ch NPs or via the mixture of dispersed MCM‐41 with preprepared Ch NPs to produce Ch NPs supported on MCM‐41. The beryllium‐uptake efficiency was studied with different pH values, contact times, and initial Be(II) concentrations. The maximum achieved uptake efficiencies of the nanocomposites (95% and 96%) were superior to that of MCM‐41 (38%) and higher than that of Ch NPs (90%). The nanocomposite formulas facilitated post‐treatment separation while maintaining a high beryllium‐uptake efficiency. The Be(II)‐uptake process for all of the materials followed the pseudo‐second‐order kinetic model and both the Langmuir and Freundlich isotherms. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46040.     

Ascorbate Oxidase Mimetic Activity of Copper(II) Oxide Nanoparticles

Although oxidase mimetic nanozymes have been widely investigated, specific biological molecules have rarely been explored as substrates, particularly in the case of ascorbate oxidase (AAO) mimetic nanozymes. Herein, we demonstrate for the first time that copper(II) oxide nanoparticles (CuO NPs) catalyze the oxidation of ascorbic acid (AA) by dissolved O₂ (as a green oxidant) to form dehydroascorbic acid (DHAA), thus functioning as a new kind of AAO mimic. Under neutral conditions, the Michaelis–Menten constant of CuO NPs (0.1302 mm ) is similar to that of AAO (0.0840 mm ). Furthermore, the robustness of CuO NPs is greater than that of AAO, thus making them suitable for applications under various conditions. As a demonstration, a fluorescence AA sensor based on the AAO mimetic activity of CuO NPs was developed. To obtain a fluorescent product, o-phenylenediamine (OPDA) was used to react with the DHAA produced by the oxidation of AA catalyzed by CuO NPs. The developed sensor was cost-effective and easy to fabricate and exhibited high selectivity/sensitivity with a wide linear range (1.25×10⁻⁶ to 1.125×10⁻⁴ m ) and a low detection limit (3.2×10⁻⁸ m ). The results are expected to aid in expanding the applicability of oxidase mimetic nanozymes in a variety of fields such as biology, medicine, and detection science.     

Ambient temperature CO oxidation over gold nanoparticles (14 nm) supported on Mg(OH)2 nanosheets

Au/Mg(OH)₂ catalysts with two different sizes (4 and 14 nm) of Au nanoparticles (NPs) have been prepared by depositing pre-fabricated Au NPs onto Mg(OH)₂ nanosheets (NSs). It was found that 14 nm Au NPs supported on Mg(OH)₂ exhibited unexpected activity for CO oxidation at ambient temperature that could be comparable with those of Au NPs of 4 nm. The Mg(OH)₂ support was suggested to be responsible for the observed catalytic activity of larger gold supported catalysts.     

Grafting of Citric Acid as a Green Coupling Agent on the Surface of CuO Nanoparticle and its Application for Synthesis and Characterization of Novel Nanocomposites Based on Poly(amide-imide) Containing N-trimellitylimido-L-valine Linkage

In this article, at first, citric acid (CA) was used as a capping agent to control the size, dispersion and morphology of copper oxide (CuO) NPs (CuO-CA). The presence of CA on the surface of CuO NPs was confirmed by Fourier transform infrared spectroscopy and thermogravimetric analyses. Then biodegradable poly(amide-imide) (PAI) was synthesized through a polycondensation reaction of N-trimellitylimido-L-valine and 4,4′-methylenebis(3-chloro-2,6-diethylaniline) in green media. PAI/CuO-CA nanocomposites (PAI/CuO-CA NCs) containing different amounts of CuO-CA NPs in the PAI matrix were prepared using an ultrasonic-assisted technique. The PAI/CuO-CA NCs obtained were characterized using different methods.     

Technology assessment of new biodegradable poly(R-3-hydroxybutyrate-co-1,4-butylene adipate) copolymers for drug delivery

New biodegradable biomaterials are attracting a huge interest as alternative to conventional polymers used in the field of drug delivery. In this work, we evaluated the ability of new biocompatible and biodegradable polyesters to form nanoparticles (NPs), and tested their potential carrier properties for controlled release of hydrophilic or lipophilic compounds. Multiblock copolymers derived from poly(R-3-hydroxybutyrate) and poly(1,4-butylene adipate) by microwave-assisted transesterification, having different chemical and physicochemical properties were tested. Nanoprecipitation was applied to obtain NPs with a homogenous size distribution. Oil Red O and calcein were encapsulated as lipophilic and hydrophilic probes, evaluating NP mean size and size polydispersity, surface charge, encapsulation efficiency, and release profile. The release curves were fitted into mathematical models to investigate the release mechanism. NPs stability appeared to be strictly related to storage conditions. The NPs were also successfully autoclaved and their mucoadhesive behavior was assessed by a “mucin-particle method.” © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47233.     

Study of antibacterial properties of polypropylene filled with surfactant‐coated silver nanoparticles

Medical applications require, in most cases, antibacterial protection. The use of silver (Ag) gives important antibacterial properties since silver is highly toxic for bacteria. In this research work, we have used silver nanoparticles (Ag NPs) with different surfactants, polyvinyl pyrrolidone (PVP) and oleic acid (OA) to facilitate dispersion. PP‐Ag NPs compounds were prepared by melt mixing, and the effects of the processing conditions on nanoparticles' dispersion were investigated by transmission electron microscopy (TEM). The antibacterial efficiency of PP‐Ag NPs compounds against Staphylococcus aureus ATCC 6538 and Escherichia coli ATCC 8379 was evaluated. Results show that good dispersion is obtained with rotating speeds in the 350–500 rpm range. TEM analysis reveals balanced dispersion and presence of some Ag NPs aggregates. Regarding antimicrobial properties, the use of PVP as surfactant leads to “significant” antimicrobial activity of 1.5 against Staphylococcus aureus and Escherichia coli; on other hand, the use of oleic acid (OA) as surfactant leads to strong protection against Staphylococcus aureus (antimicrobial activity between 2.5 and 3.3) but the overall protection against Escherichia coli is very low (lower than 1). Results show that the use of surfactants for Ag NPs has important effects on antibacterial properties of polypropylene filled with coated Ag NPs. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

The effect of Ag,ZnO, and CuO nanoparticles on the properties of the compatibilized polyethylene/thermoplastic starch blend films

In this study, the effects of Ag, ZnO, and CuO nanoparticles (NPs) on the mechanical, thermal, and biodegradability properties of the compatibilized polyethylene (PE)/thermoplastic starch (TPS) blends were investigated. Polyethylene-grafted maleic anhydride (PE-g-MA) was used as the compatibilizer. The compatibilized PE/TPS blends with different NPs were prepared by melt mixing method in a laboratory scale extruder and then pressurized in the press machine. The use of ZnO NP together with the compatibilizer in PE/TPS-based films significantly increased the tensile stress values. The use of different type NPs did not cause any significant change in the thermal stability of PE/TPS-based films. However, the effects of NPs were observed on the TPS degradation steps. The prepared films with different NPs showed an antibacterial activity between 60% and 70%. The highest crystallinity value was obtained in Ag NP containing films, among others. According to scanning electron microscopy analysis, better distribution was observed for ZnO and Ag NPs than CuO NP. In general, it can be said that the addition of NPs to PE/TPS-based blends significantly reduces the partial biodegradability of the resulting films.     

超临界流体技术构建壳聚糖纳米粒/PLLA-PEG-PLLA 复合微粒及其表征

利用离子凝胶法和超临界强制分散悬浮液(SpEDS)技术制备具有核壳型结构的壳聚糖纳米粒(CS NPs)/聚乳酸-聚乙二醇-聚乳酸三嵌段共聚物(PLLA-PEG-PLLA)复合微粒,考察和优化了壳聚糖纳米粒和复合微粒的制备条件,并对二者的理化性质和细胞毒性进行研究。结果表明,壳聚糖纳米粒的制备优化条件为壳聚糖浓度2 mg·ml^-1、pH 5.0、三聚磷酸钠浓度1 mg·ml^-1。溶剂/非溶剂比为复合微粒粒径的显著影响因素,复合微粒的制备优化条件为油相浓度5 mg·ml^-1、水油比0.75:10.00、溶液流速2 ml·min^-1、溶剂/非溶剂比0.5:1.0。优化条件制得的复合微粒粒径为323.7 nm,透射电镜(TEM)显示其具有核壳型结构。理化表征结果显示壳聚糖与三聚磷酸钠发生作用,但制备工艺前后材料官能团未发生明显变化,而且复合微粒中PLLA-PEG-PLLA晶型更加均匀;不同浓度组的CS NPs/PLLA-PEG-PLLA复合微粒(0.25、0.50和1.00 mg·ml^-1)的细胞相对增殖率分别为105.3%、101.9%和100.9%,细胞毒性分级为0级,表明具有核壳结构的CS NPs/PLLA-PEG-PLLA复合微粒生物相容性良好,有望进一步应用于共载基因和抗癌药物的抗癌活性研究。     

Plasmon enhanced upconversion luminescence of NaYF(4):Yb,Er@SiO(2)@Ag core-shell nanocomposites for cell imaging

NaYF(4):Yb,Er@SiO(2)@Ag core-shell nanocomposites were prepared to investigate metal-enhanced upconversion luminescence. Two sizes (15 and 30 nm) of Ag nanoparticles were used. The emission intensity of the upconversion nanocrystals was found to be strongly modulated by the presence of Ag nanoparticles (NPs) on the outer shell layer of the nanocomposites. The extent of modulation depended on the separation distance between Ag NPs and upconversion nanocrystals. The optimum upconversion luminescence enhancement was observed at a separation distance of 10 nm for Ag NPs with two different sizes (15 and 30 nm). A maximum upconversion luminescence enhancement of 14.4-fold was observed when 15 nm Ag nanoparticles were used and 10.8-fold was observed when 30 nm Ag NPs were used. The separation distance dependent emission intensity is ascribed to the competition between energy transfer and enhanced radiative decay rates. The biocompatibility of the nanocomposites was significantly improved by surface modification with DNA. The biological imaging capabilities of these nanocomposites were demonstrated using B16F0 cells.     

Size-dependent adsorption and conformational changes induced in bovine serum albumin (BSA) on exposure to titanium dioxide (TiO2) nanoparticles

In this study, TiO₂ nanoparticles (NPs) of different sizes were synthesized using sol gel method and calcined at different temperatures ranging from 200 to 700°C. The specific surface area of TiO₂ was found to decrease with the increase in calcination temperature. It was observed that adsorption of bovine serum albumin (BSA) on TiO₂ NPs obeyed the Freundlich adsorption isotherm, and the isotherm parameters were calculated from equilibrium adsorption batch experiments. The kinetics of adsorption was best fitted by pseudo-first-order kinetic model. The effect of particle dosage on BSA adsorption was also studied and it was observed that the adsorption increased with the increase in particle dosage and decrease in particle size. The conformational changes of BSA on exposure to TiO₂ NPs of various sizes were investigated using circular dichroism spectropolarimetry. The results suggested that BSA underwent a distortion in the secondary structure which was quantified by the percent α-helicity. A size-dependent distortion was observed. The α-helix content changed from 32.3% for pure BSA to 21.9% when exposed to NPs calcined at 200°C (350 mg/L) and to 28.4% for NPs calcined at 700°C at the same concentration.     

Incorporation of high oil content in polyvinyl acetate nanoparticles produced by batch miniemulsion polymerization stabilized with a polymeric stabilizer

Nanoparticles (NPs) have been widely applied in the biomedical area. In order to satisfy the requirements for biomedical applications, sodium lauril sulfate (SLS) and hexadecane, widely used as anionic surfactant and co‐stabilizer, were successfully replaced by biocompatible compounds, in order to obtain poly(vinyl acetate) (PVAc) NPs via miniemulsion polymerization. The incorporation of high oil content in PVAc NPs was investigated, using different poly(vinyl alcohol) (PVOH) concentrations as polymeric surfactant. Besides the polymeric surfactant, lecithin and Miglyol 812, a triacylglycerol of saturated fatty acids obtained from coconut oil, were used as surfactant and co‐stabilizer, respectively. A high Miglyol 812 content was incorporated in the PVAc NPs and the morphology was investigated by TEM. The influence of PVOH concentration on the droplet nucleation mechanism and final morphology of PVAc NPs was evaluated. High PVOH concentration favored micellar particle nucleation. According to the TEM images, hemispheres nanoparticles were obtained. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41365.     

Employment of ultrasonic waves for the preparation of PVA/TiO2‐BSA nanocomposites: Mechanical,thermal, and optical properties

The goal of this project is to obtain poly(vinyl alcohol) (PVA)/TiO₂‐bovine serum albumin (BSA) nanocomposite (NC) films in different weight percentages of modified TiO₂. For this purpose, to prevent the accumulation of nanoparticles (NPs) in the PVA matrix, the surface of the TiO₂ NPs was treated with the BSA molecules. To achieve this aim, ultrasonic waves were used as an environmentally friendly and green process that decrease the time of reactions, help better spreading of TiO₂ NPs and maintain dimensions of TiO₂ NPs in the nanoscale range. In the end, the features of the PVA/TiO₂‐BSA NC films were considered with a variety of techniques. The Fourier transform infrared spectroscopy, energy dispersive X‐ray, and X‐ray diffraction showed that the BSA was well placed on the surface of TiO₂ NPs. The thermal gravimetric analysis and UV‐visible results demonstrated that all the PVA/TiO₂‐BSA NC films have better thermal and optical properties than the pure PVA. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46558.     

Superhydrophobic durable coating based on UV‐photoreactive silica nanoparticles

Superhydrophobic surfaces can be obtained by tailoring both the chemistry and roughness topography, mimicking the Lotus leaf characteristics. Most of the synthetic superhydrophobic surfaces reported have been composed of micro and nanoparticles (NPs) embedded in polymer‐based coatings. The particles which tailor the topography are bonded to the base polymers by weak secondary forces. Consequently, the topography integrity is highly affected by handling and surface drag making them unsuitable for long term applications. This work is focused on promoting covalent bonding between the NPs and the base polymer to obtain durable superhydrophobic surfaces. The rough topography was achieved by ultraviolet (UV) curing of SiO₂ NPs containing a photoreactive benzophenone moiety in addition to methylated fumed silica NPs which can bind covalently to the polymer base coating, on UV radiation. The hydrophobic chemistry was obtained by fluoroalkylsilane top coating. Coating durability was evaluated using surface air drag and accelerated weathering conditions (UV radiation, humidity and temperature). Results indicated that the proposed approach resulted in superhydrophobic surfaces having high contact angle (>150°) and low sliding angle (<10°) with improved long term durability. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41122.     

银纳米微粒接枝木纤维的制备及抗菌性能研究

以聚乙烯吡咯烷酮(PVP)为稳定剂和分散剂,硼氢化钠为还原剂制备了聚乙烯吡咯烷酮-银纳米微粒(PVP-Ag NPs),并将其通过硅烷偶联剂接枝到木纤维上,得到了具有抗菌活性的木纤维。利用扫描电子显微镜(SEM)和傅里叶-红外光谱(FT-IR)对PVP-Ag NPs接枝的木纤维进行了结构形貌的表征,并且通过热重分析仪(TG)分析其热稳定性能。结果表明,PVP-Ag NPs接枝木纤维的最佳反应条件是硅烷偶联剂用量4%、偶合时间5 h及接枝时间10 h,此条件下得到PVP-Ag NPs接枝木纤维的接枝率为5.8%;PVP-Ag NPs接枝的木纤维对革兰氏阳性菌金黄色葡萄球菌、蜡状芽疱杆菌、革兰氏阴性菌大肠埃希氏菌以及耐药性细菌耐甲氧西林金黄色葡萄球菌这4种菌种的抑菌率均大于95%,此外,PVP-Ag NPs接枝到木纤维板上的抗菌效果也较好。     

Improved Stability and Catalytic Activity of Palladium Nanoparticle Catalysts using Phosphine‐Functionalized Imidazolium Ionic Liquids

Palladium nanoparticles (Pd NPs) stabilized by 6 different phosphine‐functionalized ionic liquids (PFILs) were synthesized in imidazolium‐based ionic liquids (ILs) using H_2(g) (4 bar) as a reductant. Characterization showed well‐dispersed particles of ∼3 nm (TEM) and confirmed the PFIL stabilization of the NPs (XPS). The PFILs were composed of an imidazolium functionality separated from the phosphine group by a propyl or undecyl chain. The counter anions for both FILs and IL solvents were chosen from N‐bis(trifluoromethanesulfonyl)imide (Tf₂N⁻), trifluoromethanesulfonate (TfO⁻) or hexafluorophosphate (PF₆⁻). Colloidal suspensions of the Pd NPs were employed as biphasic hydrogenation catalysts for the reduction of the olefinic bond in styrene under mild conditions (50 °C, 4 bar H_2(g), 1.5 h). The PFIL‐stabilized Pd NPs were effective hydrogenation catalysts and showed superior activity and recyclability over NPs synthesized in the absence of PFILs. Poisoning tests of the Pd NP catalysts and characterization of the electronic properties of the phosphine were also performed.     

Photodegradation of methylene blue with a titanium dioxide/polyacrylamide photocatalyst under sunlight

Hydrogels containing TiO₂ nanoparticles (NPs) have photocatalytic properties and degrade pollutants under light. In this study, a polyacrylamide (PAAm) hydrogel was synthesized with TiO₂ P25 NPs as the initiator, acrylamide as a monomer, and N,N′‐methylene bisacrylamide as a crosslinker in aqueous media under sunlight. Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy were applied to characterize the TiO₂/PAAm hydrogel. The effects of different synthetic conditions, such as the initiator concentration, crosslinker, and dilution, on swelling were investigated. The maximum swelling of the TiO₂/PAAm hydrogel was 45 g/g in the hydrogel synthesized with optimum conditions by 0.2% TiO₂. The photocatalytic degradability of the hydrogel was investigated with methylene blue (MB) as the pollutant target. Also, the effects of the pH and MB concentration were studied. Under optimum conditions, 95.00% of the MB was degraded by the TiO₂/PAAm photocatalyst after 5 h of irradiation under sunlight. The comparison of the results with those of the TiO₂ P25 powder showed that the TiO₂ NPs had better activity than the hydrogel, but unlike the hydrogel, the activity of these NPs decreased in each recycling time because of the aggregation of NPs. Finally, the hydrogel was recycled seven times without a considerable reduction in the degradation efficiency. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43386.     

Construction of Au/TiO2 Heterojunction with high photocatalytic performances under UVA illumination

Anatase TiO₂ nanoparticles (NPs) were successfully prepared through a hydrothermal approach, and Au NPs at various Au (0.1–2 wt%) contents were photodeposited onto the TiO₂ NPs surface. The photocatalytic efficiency for the Au/TiO₂ NPs for resorcinol photodegradation throughout UVA illumination was assessed. The TEM images and XPS findings indicated that the Au NPs are highly distributed onto TiO₂ surface in the metallic state. The 0.1%Au/TiO₂ NPs exhibited the highest photocatalytic efficiency of about 95.34%; however, 72.36% is given by pure TiO₂ NPs. It was found that the photodegradation rate of 0.1% Au/TiO₂ NPs exhibited 1.5 times of magnitude higher than pure TiO₂ NPs. 0.1%Au/TiO₂ NPs was considered to be the outstanding photoactive due to the ultimate efficient charge-carriers separation through charge transfer between Au and TiO₂ NPs. The Au NPs sizes, its dispersity on TiO₂ surface and surface plasmon resonance (SPR) were believed the critical factors for the higher photocatalytic performance of 0.1% Au/TiO₂ NPs. The prepared photocatalysts are found to be the promising materials for toxic organic compounds remediation and solar conversion.     

Effect of Solvent on Nanoparticle Production of β‐Carotene by a Supercritical Antisolvent Process

Production of micro‐ to nano‐sized particles of β‐carotene was investigated by means of solution‐enhanced dispersion by supercritical fluids (SEDS). β‐Carotene was dissolved in dichloromethane (DCM), N,N‐dimethylformamide (DMF), n‐hexane, or ethyl acetate, and supercritical CO₂ served as an antisolvent. The effects of the organic solvents, operating pressure, and temperature were examined. The morphologies of the particles produced by the SEDS were observed by field emission‐scanning electron microscopy and particle sizes were determined by image analysis. Irregularly shaped microparticles were produced in the system with DCM and DMF solution. Plate‐like microparticles were generated by using n‐hexane solution and irregular nanoparticles by ethyl acetate solution. The optimum operating conditions were found to be ethyl acetate as solvent in a defined pressure and temperature range.     

Synthesis of antimicrobial silver nanoparticles on silk fibers via γ‐radiation

Antimicrobial silver nanoparticles (NPs) were successfully synthesized on the surface of silk fibers via γ‐ray irradiation. The products were characterized with scanning electron microscope (SEM), energy dispersion spectrum, and X‐ray diffraction. The results revealed that the silver particles with a diameter of less than 20 nm were immobilized and well dispersed on the surface of silk fibers. The antimicrobial capability against the gram positive bacterium Staphylococcus aureus and the washing stability of the silk fibers produced with different conditions were tested and found to be excellent. The silk fibers treated with 1 mM solution and 10 kGy γ‐radiation showed 96% antimicrobial activity and still kept above 85% antibacterial activity after 10 washing cycles. Moreover, a mechanism for the formation of silver NPs on silk fibers under γ‐radiation was generally discussed. The resulting silk fibers coated with silver NPs can be useful as functional fabrics in a range of applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009