Synthesis of ZnO nanoparticles and study of their antibacterial and antifungal properties

In this paper, ZnO nanoparticles have been synthesized with and without the use of surfactants under different reaction conditions. The size of the ZnO nanoparticles varied in diameter (2 nm-28 nm) according to the reaction conditions employed. Promising particle size dependent antibacterial and antifungal activities of the ZnO nanoparticles have been observed. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Infrared spectroscopy (FTIR) techniques were used to characterize the particle size and morphology.     

ZnO／Ag纳米复合抗菌剂的分散与性能研究

以XRD、TEM、激光粒度分布对自制ZnO／Ag纳米复合抗菌剂进行表征，对其抗菌、抗藻和安全性能进行检测。结果表明：经PAAS分散后，ZnO／Ag纳米复合抗菌剂的团聚程度大大降低，分散剂PAAS的加入质量分数对ZnO／Ag纳米复合抗菌剂分散效果的影响呈抛物线状，最佳加入质量分数为48％，平均粒径为11．8nm。ZnO／Ag纳米复合抗菌剂具有优良的抗菌、抗藻和安全性能，对大肠埃希氏菌和金黄色葡萄球菌的最小抑菌浓度均为50mg／L，对小球藻菌的最小抑菌浓度为5mg／L，对小鼠的急性经口毒性的LD50为9260mg／kg，对皮肤无刺激性。     

一种环境友好润滑剂的制备及性能研究

在脂肪酸分子中引入氮，合成了一种新型的环境友好润滑添加剂NLA，利用红外光谱对其主要官能团进行了表征，通过四球试验机考察了添加剂在矿物基础油中的抗磨减摩性能与极压性能，用扫描电镜对磨痕表面形貌进行了分析，探讨了该类添加剂的极压抗磨作用机理。结果表明：该润滑添加剂在矿物油中具有优良的抗磨减摩性能，并且具有良好的防锈性能和生物降解性能，是一种新型的环境友好润滑添加剂。     

An environmentally friendly GAX cycle for panel heating: PGAX cycle

The objectives of this paper are to develop an environmentally friendly GAX cycle using NH₃–H₂O for panel heating applications (PGAX), and compare it to a single effect cycle for panel heating applications (PSE cycle). The PGAX cycle can be operated in three different modes with just one hardware — cooling, space heating and panel heating applications. The total COP of the PGAX cycle is higher than that of the PSE cycle due to the internal heat recovery in the GAX component. The UA ratio has more significant effect on the total COP of the PGAX cycle than that of the PSE cycle. The panel heating COP is more significantly affected by the absorber UA variation than the space heating COP. There should be optimum ratios of absorber UAs to provide the highest total COP for a given split ratio of the coolant mass flow rate in the PGAX cycle. The results from the parametric analysis of UA ratio can be used to obtain the best UA combination of the absorbers for given space heating and panel heating capacities. This paper provides the optimum UA values of the absorbers for a given split ratio of the coolant mass flow rate.     

Bi-functional NiO-ZnO nanocomposite: Synthesis,characterization, antibacterial and photo assisted degradation study

NiO–ZnO mixed metal oxide nanocomposite was synthesized via chemical homogeneous precipitation method. The synthesized nanocomposite was also characterized by XRD, FESEM with EDS, FTIR, and UV. XRD exhibit an average crystallite size of 29 nm. The elemental composition obtained from EDS shows a nearly equal concentration of Ni and Zn with an atomic ratio of Ni/Zn = 0.96. The particles of nanocomposite are highly stable throughout a wide range of pH. The DLS exhibit an average hydrodynamic particle size ~49 nm. The high pore diameter and pore volume of nanocomposite obtained from BET exhibited a high photocatalytic activity for the removal of methylene blue (MB) dye under UV light irradiation. The kinetics of photocatalytic reduction of MB followed the Langmuir isotherm model, suggesting homogeneous surface adsorption of MB on the surface of the nanocomposite. NiO-ZnO nanocomposite was also found to be an effective antibacterial agent against Gram positive bacteria (Staphylococcus aureus) and Gram negative bacteria (Escherichia coli). Colony forming unit plate counting method showed that 95% and 85% of S. aureus and E. coli respectively were killed by the nanocomposite. Also, this suggested that nanocomposite was more effective towards S. aureus than E. coli. Release of intracellular components was evident from FESEM image of nanocomposite-bacteria cell, cell integrity study, and cell permeability study. This included the release of electrolytes, nucleic acid, and proteins, ultimately leading to cell lysis.     

Advocating recycling and encouraging environmentally friendly habits through gamification: An empirical investigation

A circular economy emphasizes decreasing the use of new raw materials and the disposal of waste by reusing and recycling, which ensures that products and materials can remain in use, thereby extending their life cycle. Promoting recycling and environmentally friendly habits can help consumers engage in sustainability thinking, which is essential considering that effective resource recycling critically depends on environmentalists' behaviors. A helpful means to encourage such thinking and habits is gamification. Deepening and extending findings from the existing literature, this study applies gamification to conceptualize contributions to resource recycling and environmentally friendly habits. For this purpose, we integrate a cognitive–affective model with an expectation–confirmation model to examine causal relationships between the utilitarian (effectiveness and efficiency) and hedonic (playfulness) values of a website and users' cognition- and affect-based attitudes, satisfaction, confirmation, and behavioral intentions (word of mouth [WOM] and continued usage). We empirically test the research model by applying structural equation modeling to analyze the experiences of a sample of 457 participants that are members of Recyclebank, an American company set up to encourage recycling and environmentally friendly habits. The results reveal that effectiveness, efficiency, playfulness, and confirmation contribute to cognition- and affect-based attitudes and satisfaction, which in turn influence repetitive usage and WOM intentions. Attitudes, however, may differ depending on the cultural background of the user. Thus, we find that collectivistic versus individualistic user orientations moderate the effects of value on attitudes in a gamification context. The findings provide website managers with insights regarding determinants crucial in formulating intention policies and motivating users’ to continue using a service.     

Multifunctional dual Z-scheme heterostructured Sm2O3-WO3-La2O3 nanocomposite: Enhanced electrochemical,photocatalytic, and antibacterial properties

In this study, heterostructured dual Z-scheme Sm₂O₃-WO₃-La₂O₃ nanocomposite (NC) and bare Sm₂O₃, WO₃, and La₂O₃ nanostructured (NSs) were prepared using a co-precipitation approach. The comparative electrochemical, photocatalytic, and antimicrobial properties of NC and NSs were studied. The XRD spectrum exhibits the formation of bare NSs and NC having cubic-Sm₂O₃, monoclinic-WO₃, and hexagonal-La₂O₃ phases. FESEM results showed mesoporous morphology of NC. The higher electrical conductivity 261.33 mho-cm⁻¹ and lower optical energy bandgap 2.55 eV were obtained for NC. The photodegradation tests exhibited that NC photocatalyst has degraded 99% (methylene blue), 96% (Methyl orange), 99% (safranin-O), 48% (p-nitroaniline), and 98% (methyl red) dyes pollutants in 40 min sunlight radiation and showed strong inhibition activity against E. coli, K. pneumoniae, S. aureus, P. Vulgaris, and P. aeruginosa bacterial strains with zones of inhibition (ZOI) 31 mm, 30 mm, 30 mm, 28 mm, and 31 mm, respectively. Electrochemical studies revealed the excellent capacitive characteristics of NC with a specific capacitance 532F/g at a scan rate 5 mV/s, energy density 48.0278 W h Kg⁻¹, and power density 0.3782 KW Kg⁻¹ at 0.006 A/cm² current density. Furthermore, the present study revealed a novel composition for environmental remediation and energy storage applications.     

溶胶-凝胶法合成ZnO纳米材料及其抗菌性能研究

采用溶胶-凝胶法制备氧化锌纳米材料并考察了其抗菌性能.研究发现,通过调控醋酸锌-无水乙醇-氢氧化钠反应体系的反应温度、反应时间、反应物浓度以及反应体系中的水含量可以控制纳米ZnO的粒径分布;以金黄色葡萄球菌和大肠杆菌作为革兰氏阳性菌和革兰氏阴性菌的代表,用抑菌圈法考察了材料的抗菌性能,结果表明,溶胶-凝胶法合成的ZnO纳米材料抑菌效果明显优于相应的水热法产物和市售产品,且与其粒径分布密切相关;在实验条件下,ZnO材料对大肠杆菌和金黄色葡萄球菌的抑制性能随ZnO纳米材料的粒径增大在5nm左右出现一个极值,材料的粒径小于或大于5nm,其抗菌效果均变差.     

Ag/TiO2/bentonite nanocomposite for biological applications: Synthesis,characterization, antibacterial and cytotoxic investigations

Bentonite (bent) clay supported silver (Ag)/titanium dioxide (TiO₂) nanocomposite material was green synthesized by facile thermal decomposition method in the absence of reducing and precipitating agents. The samples were characterized by XRD, BET, HR-SEM with EDX mapping, TEM with SAED patterns, XPS, PSA, FT-IR, and UV–Vis DRS. XRD and EDX spectra showed peaks of Ag and TiO₂, confirming the formation of the Ag/TiO₂ nanoparticles in the composite. TEM revealed the uniform distribution of Ag/TiO₂ nanoparticles cluster on the surface of the bent with an average size of ～5 to 50 nm. The antibacterial activities of Na-bent, Ag, TiO₂, and Ag/TiO₂/bent nanocomposite samples were tested against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) bacteria by the well diffusion method. Furthermore, the cytotoxicity of Ag/TiO₂/bent nanocomposite material was determined by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Also, the succinate-dehydrogenase release showed the nontoxic nature of the nanocomposite at low concentrations. The cytotoxicity results of samples were evaluated using human embryonic kidney cell line (HEK 293) and have given excellent biocompatibility and cell proliferation in the in vitro studies.     

Immobilization of ZnO on Chitosan-Neem seed composite for enhanced thermal and antibacterial activity

Natural and inorganic materials of Chitosan-Zinc oxide-Neem seed (CS-ZnO-NS) hybrid composite were synthesized by chemical precipitation method. The obtained CS-ZnO-NS hybrid composites were characterized for functional group confirmation by Fourier transform infrared spectroscopy and UV–Visible spectroscopy. The ZnO particles connected to biopolymers exhibited small grains and rod, bullet like structure confirmed by scanning electron microscopy and transmission electron microscopy analysis. The size of the prepared CS-ZnO-NS hybrid composite was found to be 20–80?nm. The crystalline behaviors were determined by X-ray diffraction analysis. The surface area of the prepared hybrid composite was determined using BET analysis. The elemental composition was analyzed by energy dispersive X-ray spectroscopy and thermal behaviors by thermo gravimetric analysis. The obtained result shows that zinc oxide was well able to incorporate into chitosan-neem seed composite which enhances the thermal stability. Further, the antibacterial activity evaluated by agar well diffusion method against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria exhibits higher inhibition effect because of ZnO particles presence in the chitosan-neem seed. Hence the CS-ZnO-NS is a promising material for biomedical applications.     

Synthesis of Ag+/CaTiO3:Pr3+ with luminescence and antibacterial properties

In the study, CaTiO₃:Pr³⁺ and Ag⁺ nano-particles-coated CaTiO₃:Pr³⁺ red-emitting phosphors were synthesized by the citric acid sol combustion method. The photoluminescence properties and microstructures were investigated by photoluminescence spectroscopy, X-ray powder diffraction, and scanning electron microscopy. All samples showed the consistent orthorhombic crystal structure with standard CaTiO₃. The photoluminescence measurements indicated that the all the experimental samples synthesized at 800?°C could be excited by 323?nm ultraviolent light and the emission intensity reached its maximum value at 619?nm. The Ag⁺ coating on the grain surface of CaTiO₃:Pr³⁺ red-emitting phosphors had the antibacterial properties and the sample synthesized at 800?°C had optimal antibacterial properties. Moreover, the antibacterial property increased with the increase in the addition of Ag⁺ coating. The Ag⁺-coated CaTiO₃:Pr³⁺ red-emitting phosphor excited by ultraviolent radiation is a promising red phosphor for manufacturing white-light-emitting diodes as well as antibacterial materials. This multi-functional material can be applied in many areas such as medical devices.     

Preparation and high-temperature tribological properties of CrAlVYN-Ag nanocomposite coatings

CrAlVYN-Ag coatings were successfully deposited by introducing the elements of V and Ag into CrAlYN hard coatings. Their microstructure and mechanical property as a function of the annealing temperature were investigated from room temperature (RT) (～25°C) to 800°C. Besides, the worn surfaces were analyzed after combined effects of temperature and friction to figure out the wear mechanisms at different temperatures. The coatings exhibited special surface morphologies and Ag diffusion after annealing at different temperatures. In addition, the x-ray diffraction results showed that the coatings suffered obvious oxidation once the temperature exceeded 600°C; as a result of this, the coating hardness decreased sharply. The friction coefficients were relatively high during the tribological tests from RT to 400°C because the abrasive wear mechanisms played a dominant role. The lower friction coefficients obtained at 600 and 700°C were mainly due to the self-lubricating mechanisms. However, the coating exhibited higher friction coefficient at 800°C, which was mainly ascribed to the severe oxidation wear of the coating.     

Self-assembly of the Ag deposited ZnO/carbon nanospheres: A resourceful photocatalyst for efficient photocatalytic degradation of methylene blue dye in water

Carbon nanospheres (CNSs) are synthesized by pyrolysis of benzene at 1000?°C. Various UV-light photocatalysts of ZnO/CNSs and Ag-ZnO/CNSs (AZCN) composites are synthesized on the surface of CNSs using a facile chemical precipitation method. Morphological and optical properties of the as-synthesized photocatalysts are characterized by scanning electron microscopy, X-ray diffraction, energy dispersive spectroscopy, UV-Vis spectroscopy, photoluminescence and Raman spectroscopy. Photocatalytic degradation efficiency of methylene blue dye is investigated to examine the photocatalytic activity of synthesized photocatalysts. It is found that as-synthesized ZnO/CNSs composite can degrade higher methylene blue dye (～85.6%) after 25?min of UV irradiation in comparison with that of CNSs. A prominent improvement in the photodegradation is attained by depositing metal (Ag) particles on the surface of ZnO/CNSs composite. AZCN composite displays the enhanced photocatalytic degradation performance (～95% after 15?min of UV light) in high concentration of methylene blue dye. Furthermore, stability performance is studied by recycling the AZCN composite photocatalyst. It is found that the photocatalytic activity of AZCN composite is only slightly decreased even after five cycles. Present work demonstrates that AZCN composite show a great potential in the treatment of organic pollutants for wastewater treatment.     

Influence of aqueous medium on mechanical properties of conventional and new environmentally friendly regenerated cellulose fibers

Comparative investigations between the new lyocell fibers and the regular viscose and modal types were made in order to explain the reasons for the differences in the mechanical properties of the fibers. The purpose was a systematic analysis of structure characteristics and of influence of aqueous medium on the mechanical properties. The properties determined in the wet state reflect the effect of the aqueous medium on the changes in the supermolecular structure during wet treatments [1, 2]. The new lyocell fibers consist of longer molecules and have a higher degree of crystallinity. Smaller but longer crystallites are oriented in the fiber axis direction and the voids structure is similar to that of viscose fibers [3]. Good mechanical properties are conditioned by the structure of the lyocell fibers, above all by high values of the orientation factor and crystallinity index. Sorption properties place lyocell fibers between the viscose and modal fibers. The water influence on the mechanical properties of lyocell fibers is considerably smaller compared to the viscose and modal fibers. Received: 18 September 2000 / Reviewed and accepted: 20 September 2000     

Facile synthesis of Ag/ZnO nanorods using Ag/C cables as templates and their gas-sensing properties

A solid-state chemical reaction with the assistance of Ag/C nanocables was implemented for the preparation of Ag/ZnO nanorods. This is the first time Ag/ZnO nanorods are fabricated by using Ag/C cables as template. Compared with the traditional organic surfactant, Ag/C cable is a new and effective template to control the shape of precursors in the solid-state reaction under ambient conditions. The results of systematical gas-sensing studies demonstrate that the sensor based on Ag/ZnO nanorod materials has high sensitivity, good selectivity and short response and reversion time to ethanol. It demonstrates that Ag/ZnO nanorods can be used as gas-sensing material.     

Investigation of structural,optical, antibacterial,and dielectric properties of V-doped copper oxide thin films: Comparison with undoped copper oxide thin films

Vanadium doped Copper oxide (CO) thin films were prepared by the sol-gel dip-coating method. The properties of thin films were examined by X-Ray Diffractometer (XRD), UV–Visible-NIR spectrophotometry, and dielectric properties analyzer. The antibacterial and photocatalytic properties were also determined. XRD spectra revealed the dual-phase of copper oxide (cuprite and tenorite) for all percentages of V with no other impurity peak. Tauc's relation is used to probe the optical band gap which is reduced from 1.96 to 1.64 eV with an increase in vanadium doping percentage. The impurity band coalesces with the conduction band of copper oxide to decrease the band gap. Dielectric constant measurements reveal that the Ac conductivity of thin films increases with an increase in V doping percentage.     

Galbanic acid,a sesquiterpene coumarin as a novel candidate for the biosynthesis of silver nanoparticles: In vitro hemocompatibility,antiproliferative, antibacterial,antioxidant, and anti-inflammatory properties

In the current study, silver nanoparticles (AgNPs) were biosynthesized using galbanic acid (GA), a sesquiterpene coumarin. The formation of GA-AgNPs was characterized by ultraviolet–visible (UV–Vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), Energy Dispersive X-ray (EDX), and X-ray diffraction (XRD). The biosynthesized GA-AgNPs were spherical in shape with an average particle size of 142.33 ± 32.6 nm. The results from the antibacterial assays suggested that biosynthesized GA-AgNPs were more potent against multi-drug resistant (MDR) and non-MDR pathogenic bacteria than the crude GA alone. The nanoparticles also showed potent antiproliferative potential against H1229 and MCF-7 cancer cells with IC50 values of 25 μg/mL and 50 μg/mL by the MTT assay, respectively. These NPs showed good antioxidant (30 % at 100 µg/mL), anti-inflammatory (99.5 % at 500 µg/mL), and anti-coagulant properties without significant hemolysis on red blood cells (RBCs). These results confirm the benefits of using the green, simple, and cost-effective manner for the synthesis of AgNPs with excellent biological properties and hemocompatibility.     

Ultrasonic synthesis of the microporous metal-organic framework Cu3(BTC)2 at ambient temperature and pressure: An efficient and environmentally friendly method

A three-dimensional (3-D) metal-organic framework (MOF) with 3-D channels, i.e. Cu₃(BTC)₂ (HKUST-1, BTC = benzene-1,3,5-tricarboxylate), was synthesized by using ultrasonic method for the first time. The reaction of cupric acetate and H₃BTC in a mixed solution of DMF/EtOH/H₂O (3:1:2, v/v) under ultrasonic irradiation at ambient temperature and atmospheric pressure for short reaction times (5-60min) gave Cu₃(BTC)₂ in high yields (62.6-85.1%). These Cu₃(BTC)₂ nano-crystals have dimensions of a size range of 10-200 nm, which are much smaller than those synthesized using conventional solvothermal method. There were no significant differences in physicochemical properties, e.g. BET surface area, pore volume, and hydrogen storage capacity, between Cu₃(BTC)₂ nano-crystals prepared using ultrasonic method and the microcrystals obtained by using improved solvothermal method. Compared with traditional synthetic techniques, such as solvent diffusion technique, hydrothermal and solvothermal methods, ultrasonic method for the construction of porous MOFs was found to be highly efficient and environmentally friendly.     

Electrical and optical properties of ZnO:Mn thin films grown by MOCVD

Diluted magnetic semiconductor epitaxial thin films of Zn_1 − xMn_xO have been grown on c-sapphire by the MOCVD technique. Variations of a and c lattice parameters follow Vegard's law and attest to the incorporation of substitutional Mn²⁺ ions. Carrier concentration (n-type) and electron mobility were studied versus temperature for different concentrations of manganese. Incorporation of manganese leads to the opening of the band gap, observed as a blue shift in energy regarding pure ZnO.     

Colloidal templating for producing hollow ZnO shells: Fabrication, growth and electrical properties

Colloidal templating and pulsed laser deposition (PLD) have been combined to fabricate arrays of ordered two-dimensional hollow ZnO shells. Templates were formed by spin-coating colloidal solutions containing monodispersed polymethylmethacrylate (PMMA) beads. The optimum condition for forming templates of ordered two-dimensional geometry was deduced by calculating the radial distribution functions. On templates ZnO films were deposited by a PLD method. Upon annealing ZnO films crystallize into a würtzite structure. The surface morphology of hollow ZnO shells consists of protruding columnar nano-crystallites with no distinct ZnO texture. The electrical properties were measured as a function of annealing temperature. The electrical conductivity increases with increase in annealing temperature. The activation energy was estimated to be 0.7 eV. The change in the electrical properties upon grain growth has been attributed to alteration in the fraction site availability for defect formation at the grain boundaries.