Facile synthesis of Ag/ZnO microstructures with enhanced photocatalytic activity

In this paper, we developed a facile low-temperature solution route to prepare radical-shaped ZnO microprisms and to deposit metal silver on the surface of ZnO to form Ag/ZnO microstructures. The samples were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectroscopy. Experimental results show that the deposition of metal Ag nanospecies can be achieved successfully by simply aging the solution at 75 °C, and the radical-shaped microstructures of ZnO are well maintained. The Ag/ZnO microstructures exhibit much lower PL emission intensity and much higher photocatalytic activity than those of radical-shaped ZnO microprisms.     

Facile synthesis of magnetic iron oxide nanoparticles and their characterization

Magnetic iron oxide nanoparticles are synthesized by suitable modification of the standard synthetic procedure without use of inert atmosphere and at room temperature. The facile synthesis procedure can be easily scaled up and is of important from industrial point of view for the commercial large scale production of magnetic iron oxide nanoparticles. The synthesized nanoparticles were characterized by thermal, dynamic light scattering, scanning electron microscopy and transmission electron microscopy analyses.     

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.     

Generic synthesis and versatile applications of molecularly organic-inorganic hybrid mesoporous organosilica nanoparticles with asymmetric Janus topologies and structures

Precise control over the morphology,nanostructure,composition,and particle size of molecularly organic-inorganic hybrid mesoporous organosilica nanoparticles (MONs) still remains a major challenge,which severely restricts their broad applications.In this work an efficient bridged organic group-determined growth strategy has been proposed for the facile synthesis of highly dispersed and uniform MONs with multifarious Janus morphologies,nanostructures,organic-inorganic hybrid compositions,and particle sizes,which can be easily controlled simply by varying the bridged organic groups and the concentration of bis-silylated organosilica precursors used in the synthesis.In addition,the formation mechanism of Janus MONs determined by the bridged organic group has been discussed.Based on the specific structures,compositions,and asymmetric morphologies,all the synthesized Janus MONs with hollow structures (JHMONs) demonstrate excellent performances in nanomedicine as desirable drug carriers with high drug-loading efficiencies/capacities,pH-responsive drug releasing,and enhanced therapeutic efficiencies,as attractive contrastenhanced contrast agents for ultrasound imaging,and as excellent bilirubin adsorbents with noticeably high adsorption capacities and high blood compatibilities.The developed versatile synthetic strategy and the obtained JHMONs are extremely important in the development and applications of MONs,particularly in the areas of nanoscience and nanotechnology.     

Facile synthesis of Ag nanoparticles supported on TiO2 inverse opal with enhanced visible-light photocatalytic activity

TiO₂ inverse opal films loaded with silver nanoparticles (ATIO) were synthesized on glass substrates. TiO₂ inverse opal (TIO) films were prepared via a sol-gel process using self-assembly of SiO₂ colloidal crystal template and a facile wet chemical route featuring an AgNO₃ precursor solution to fabricate silver nanoparticles on the TIO films. The inverse opal structure and Ag deposition physically and chemically modify titania, respectively. The catalysts were characterized by Raman spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), UV-vis absorption spectra, X-ray photoelectron spectroscopy and photoluminescence spectroscopy. The HRTEM results show that Ag nanoparticles measuring 5-10 nm were evenly distributed on TIO. Both the UV- and visible-light photocatalytic activities of the samples were evaluated by analyzing the degradation of methylene blue (MB) in aqueous solution. The results reveal that the apparent reaction rate constant (k_app) of MB degradation of the sample ATIO under UV-light irradiation is approximately 1.5 times that of the conventional Ag-loaded TiO₂ film (ATF) without an ordered porous structure at an AgNO₃ concentration of 5 mM in the precursor solution. At an AgNO₃ concentration of 10 mM, the sample exhibits a k_app value approximately 4.2 times that of ATF under visible-light irradiation. This enhanced visible-light photocatalytic performance can be attributed to the synergistic effect of optimized Ag nanoparticle deposition and an ordered macroporous TIO structure. Repeated cycling tests revealed that the samples showed stable photocatalytic activity, even after six repeated cycles.     

Ag/低分子量壳聚糖复合胶乳的制备及抗菌性能

采用原位法和液相化学还原法制备了Ag/低分子量壳聚糖(LMWC)和Ag/LMWC-聚吡咯(PPy)复合胶乳,分析了各种工艺条件对复合胶乳中纳米Ag粒子粒径及粒度分布的影响规律,并确定了复合胶乳较适宜的合成条件。采用UV-Vis、TEM、FTIR及 XRD对复合胶乳的组成和纳米Ag的形态进行了表征。结果显示: Ag/LMWC 和 Ag/LMWC-PPy复合胶乳中的纳米Ag晶体为面心立方结构,平均粒径约为10~20 nm。抗菌测试结果表明: LMWC(黏均分子量M_η=4.3×10⁵)的抗菌效果优于未降解的原始壳聚糖(CS),由于纳米Ag的引入,Ag/LMWC和Ag/LMWC-PPy复合胶乳对大肠杆菌和金黄色葡萄球菌与单一的LMWC相比均具有较高的抑菌活性。     

Characterisation and antifungal activity of silver nanoparticles biologically synthesised by Amaranthus retroflexus leaf extract

ABSTRACT

Following the emergence of resistant fungal pathogens, silver nanoparticles (AgNPs) biosynthesized by plants have been recognized as promising tools to combat parasitic fungi. This study evaluated the potency of Amaranthus retroflexus in producing AgNPs, followed by testing their antifungal effects. The AgNPs exhibited a maximum absorption at 430 nm through ultraviolet-visible spectroscopy, while the X-ray diffraction indicated that they were crystal in nature. Fourier transform infrared spectroscopy confirmed the conversion of Ag⁺ ions to AgNPs due to the reduction by capping material of plant extract. The transmission electron microscope analysis further revealed that the AgNPs were spherical ranging from 10 nm to 32 nm in size. The AgNPs at the concentrations of 50, 100, 200, and 400 μg/mL were applied to the growth of plant, mushroom, and human pathogenic fungi. The 50% minimum inhibitory concentrations (MIC₅₀) against Macrophomina phaseolina, Alternaria alternata and Fusarium oxysporum were observed to be 159.80 ± 14.49, 337.09 ± 19.72, and 328.05 ± 13.29 μg/mL, respectively. However, no considerable inhibition was observed regarding Trichoderma harzianum or Geotrichum candidum. These findings may suggest A. retroflexus as a green solution for biosynthesizing AgNPs with potent antifungal activities against plant pathogenic fungi.     

Facile synthesis and enhanced photocatalytic activity of hierarchical porous ZnO microspheres

In this paper, hierarchical porous ZnO microspheres were successfully synthesized by calcining the microspheric zinc hydroxide carbonate (ZHC) precursor, which were the precipitate products of a hydrothermal reaction by zinc nitrate hexahydrate and urea in the presence of trisodium citrate. The as-prepared ZnO microspheres with diameters of 4-5 μm were assembled by numerous porous nanosheets which had the uniform thickness of about 10 nm. The photocatalytic activity of the ZnO microspheres was evaluated by photodegradation reaction of methylene blue (MB). The as-prepared ZnO microspheres exhibited a significantly enhanced photocatalytic activity than commercial ZnO and TiO₂. This was mainly attributed to the larger specific surface area and stability against aggregation.     

Facile solvothermal synthesis of NiFe2O4 nanoparticles for high-performance supercapacitor applications

We report a green and facile approach for the synthesis of NiFe₂O₄ (NF) nanoparticles with good crystallinity. The prepared materials are studied by various techniques in order to know their phase structure, crystallinity, morphology and elemental state. The BET analysis revealed a high surface area of 80.0 m²·g⁻¹ for NF possessing a high pore volume of 0.54 cm³·g⁻¹, also contributing to the amelioration of the electrochemical performance. The NF sample is studied for its application in supercapacitors in an aqueous 2 mol·L⁻¹ KOH electrolyte. Electrochemical properties are studied both in the three-electrode method and in a symmetrical supercapacitor cell. Results show a high specific capacitance of 478.0 F·g⁻¹ from the CV curve at an applied scan rate of 5 mV·s⁻¹ and 368.0 F·g⁻¹ from the GCD analysis at a current density of 1 A·g⁻¹ for the NF electrode. Further, the material exhibited an 88% retention of its specific capacitance after continuous 10000 cycles at a higher applied current density of 8 A·g⁻¹. These encouraging properties of NF nanoparticles suggest the practical applicability in high-performance supercapacitors.     

Facile synthesis of Au/ZnO nanoparticles and their enhanced photocatalytic activity for hydroxylation of benzene

Au/ZnO nanocomposites have been prepared by a simple chemical method. For the first time, the nanocomposites were directly used as photocatalysts for hydroxylation of aromatic hydrocarbons under UV and visible light irradiation. The results show that the as-prepared photocatalysts display high photocatalytic activity for UV and visible catalytic hydroxylation of benzene. Without the assistance of any solvent or additive, high selectivity and high conversion efficiency were still obtained. Different photocatalytic mechanisms were proposed depending on whether excitation happens on ZnO semiconductor or on the surface plasmon band of Au. The former is Au nanoparticles act as electron buffer due to irradiation by UV light and ZnO nanoparticles as reactive sites for hydroxylation of benzene, the latter is that Au nanoparticles act as light harvesters and inject electrons into ZnO conduction band and as photocatalytic sites under visible light irradiation.     

Development of topical hydrogels of terbinafine hydrochloride and evaluation of their antifungal activity

The purpose of this study was to prepare hydrogels and microemulsion (ME)-based gel formulations containing 1% terbinafine hydrochloride (TER-HCL) and to evaluate the use of these formulations for the antifungal treatment of fungal infections. Three different hydrogel formulations were prepared using chitosan, Carbopol® 974 and Natrosol® 250 polymers. A pseudo-ternary phase diagram was constructed, and starting from ME formulation, a ME gel form containing 1% Carbopol 974 was prepared. We also examined the characteristic properties of the prepared hyrogels. The physical stability of hydrogels and the ME -based gels were evaluated after storage at different temperatures for a period of 3 months. The release of TER-HCL from the gels and the commercial product (Lamisil®) was carried out by using a standard dialysis membrane in phosphate buffer (pH 5.2) at 32?°C. The results of the in vitro release study showed that the Natrosol gel released the highest amount of drug, followed by Carbopol gel, chitosan gel, commercial product, and the microoemulsion-based gel in that order. In vitro examination of antifungal activity revealed that all the prepared and commercial products were effective against Candida parapsilosis, Penicillium, Aspergillus niger and Microsporum. These results indicate that the Natrosol®-based hydrogel is a good candidate for the topical delivery of TER-HCL.     

Facile synthesis of Ni-doped SnO2 nanorods and their high gas sensitivity to isopropanol

In this work, pure SnO₂ and Ni-doped SnO₂ nanorods were synthesized through a one-step template-free hydrothermal method and then used to detect isopropanol. Sensors fabricated with the Ni-doped SnO₂ nanocomposites showed the best gas sensing performance when the Ni doping amount was 1.5 mol.%. The response reached 250 at 225 °C, which was approximately 8.3 times higher than that of the pure SnO₂ nanorods. The limit of detection for isopropanol was as low as 10 ppb at the optimum working temperature. In addition, it also displayed good selectivity and excellent reproducibility. It is believed that the enhanced isopropanol sensing behavior benefit from the increased oxygen defects and larger specific surface area by Ni doping.     

Ultrasonic-assisted synthesis of ZnO/NiO nanocomposites and kinetic study of their photocatalytic activity

In the present study, a facile ultrasonic-assisted method was developed for the synthesis of ZnO/NiO nanocomposites. The X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, diffuse reflectance spectroscopy and Fourier transform infrared spectroscopy techniques was applied for characterization of structure, purity, morphology and optical properties of the resultant samples. The photocatalytic performance of the synthesized ZnO/NiO nanocomposites was evaluated by monitoring the photodegradation of Rhodamine B (RhB) under UV light irradiation. Moreover, the influence of various parameters, such as molar percentage of NiO to ZnO, initial RhB concentration, pH of solution and photocatalyst weight was studied. The results show that the photocatalytic activity of the ZnO/NiO nanocomposite was higher than that of pure ZnO and NiO.     

含纳米银的明胶/壳聚糖纳米纤维的制备及其抗菌性能研究

以浓度为88%的甲酸溶液作为纺丝溶剂,采用静电纺丝和紫外光照射还原的方法制备了含纳米银颗粒的明胶/壳聚糖纳米纤维。研究发现,壳聚糖的加入量低于明胶质量的3/16时可以得到纳米纤维,纤维平均直径随着硝酸银加入量的增大而减小,纤维表面纳米银的平均直径随着硝酸银加入量的增大而增大,在纺丝体系中硝酸银的加入量存在一个极限值。所制得含纳米银的明胶/壳聚糖纳米纤维对金黄色葡萄球菌和绿脓杆菌具有较好的抑菌性能,纺丝时加入1%硝酸银制得纳米纤维膜的抑菌率达到99%以上,这种抗菌型纳米纤维可以应用于医用敷料等领域。     

Enhanced antibacterial activity and mechanism studies of Ag/Bi2O3 nanocomposites

In this work, sphere-like Ag/Bi₂O₃ nanocomposites with the average size of ca. 170?nm were successfully synthesized by simple deposition-precipitation method. The antibacterial activities of as-prepared Ag/Bi₂O₃ nanocomposites were evaluated by minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and colony counting methods. It was found that Ag/Bi₂O₃ nanocomposites displayed greatly improved antibacterial ability against common pathogenic Gram-positive and Gram-negative bacteria in comparison with single-component Bi₂O₃ nanospheres. More importantly, Ag/Bi₂O₃ nanocomposites exhibited remarkably outstanding antibacterial activities against clinical drug-resistant bacteria. The antibacterial activity of Ag/Bi₂O₃ nanocomposite increased with the increase of Ag content and 15?wt% Ag/Bi₂O₃ nanocomposites showed the highest antibacterial activity. Furthermore, a plausible antibacterial mechanism of Ag/Bi₂O₃ nanocomposite was proposed. It was believed that the enhanced generation of H₂O₂ could lead to the membrane leakage of cytosol and the inactivation of respiratory chain dehydrogenaes, which was possibly responsible for the enhanced antibacterial activities of nanocomposites.     

Facile synthesis of Ag/ZnO heterostructures assisted by UV irradiation: Highly photocatalytic property and enhanced photostability

We report a new method to synthesize Ag/ZnO heterostructures assisted by UV irradiation. The formation of Ag/ZnO heterostructures depends on photogenerated electrons produced by ZnO under UV light to reduce high valence silver. Functional property of the Ag/ZnO heterostructures is evaluated by photodegradation of methylene blue (MB) under UV illumination. Results of photodegradation tests reveal that the optimal photocatalytic activity of as-syntheszied samples is about 1.5 times higher than the pure ZnO synthesized in the same condition or commercial TiO₂ (P-25), showing the advantage of the unique structure in the Ag/ZnO heterostructure. Besides, due to the reduced activation of surface oxygen atom, photocatalytic activity of the photocatalysts has no evident decrease even after three recycles.     

载银纳米TiO2抗菌剂的制备及抗菌性能研究

采用四氯化钛自生晶种水解法制备了纳米TiO2，通过在水解过程中引入硝酸银制得载银纳米TiO2。对载银前后的纳米TiO2进行了XRD和TEM表征。XRD图谱表明，纳米TiO2属于锐钛矿晶型结构，水解过程中加入硝酸银得到纳米TiO2与氯化银的复合体（AgCl／TiO2）。TEM照片显示，纳米TiO2样品为分散较好的20-30nm之间的粒子，而载银后的复合物粒子明显增大，有轻度的团聚发生。采用抑菌环、悬浮液浊度法测定了载银前后纳米TiO2的抗菌性能，结果表明，AgCl／TiO2抗菌材料对金黄色葡萄球菌有明显的抑菌效果，其最小抑菌浓度为750mg／L。达到日本制定的“银等无机抗菌剂自主规格及其抗菌实验法”规定的〈800mg／L指标。     

Effect of Sn precursor on the synthesis of SnO2 and Sb-doped SnO2 particles via polymeric precursor method

SnO2 and Sb-doped SnO2 particles were synthesized using the polymeric precursor method with different Sn salt precursors： SnCl2.2H2O, SnCl4.5H20, or Sn citrate. Sb2O3 was used as the precursor of Sb, and the molar ratio of nsn：nsb was held constant. FTIR and TGA/DTA were used to examine the influence of the Sn precursor on the formation and thermal decomposition of the Sn and Sn-Sb complexes. The calcination products obtained from heating the Sn and Sn-Sb complexes at 500℃ in air were analyzed using XRD and TEM analysis. The results revealed that the SnO2 and Sb-doped SnO2 formation temperatures depended on the nature of the Sn precursor. The calcination products were found to be SnO2 and Sb-doped SnO2 particles, which crystallized in a tetragonal cassiterite structure with a highly preferred （110） planar orientation. The Sn precursor and the presence of Sb in the SnO2 matrix strongly influenced the crystallinity and lattice parameters.     

Facile synthesis of MnCO3 hollow dumbbells and their conversion to manganese oxide

Manganese carbonate (MnCO₃) hollow dumbbells were synthesized via a polyol process. Based on the structural analysis of the samples obtained at different reaction times, a mechanism of nucleation-growth-aggregation-ripening was proposed to account for the formation of the hollow dumbbells. Moreover, the manganese oxide has also been obtained from the MnCO₃ crystals after thermal transformation in laboratory air, and the phase of final product could easily be controlled to be either MnO₂ or Mn₂O₃, simply by altering the calcination conditions. The manganese oxide powder products possessed mesoporosity and essentially preserved the pristine morphology of the MnCO₃ precursor.     

Green synthesis of silver nanoparticles using aqueous solution of Ficus benghalensis leaf extract and characterization of their antibacterial activity

The present study reports an environmentally friendly and rapid method for synthesis of silver nanoparticles. Although several articles have been reported for the synthesis of silver nanoparticles from plant extract, here we have developed a green synthetic method for silver nanoparticles using Ficus benghalensis leaf extract which acts as a reducing and capping agent. It was observed that use of Ficus benghalensis leaf extract makes a fast and convenient method for the synthesis of silver nanoparticles and can reduce silver ions into silver nanoparticles within 5 min of reaction time without using any harsh conditions. Silver nanoparticles so prepared were characterized by using UV-visible spectroscopy, transmission electron microscope-energy dispersive spectra (TEM-EDS) and X-ray diffraction (XRD). Further, these nanoparticles show effective antibacterial activity toward E.coli MTCC1302 due to high surface to volume ratio.