凝胶网格控制合成纳米ZnO及其光催化活性

以明胶为反应介质,采用凝胶网格控制合成法制备了单分散球形纳米ZnO光催化剂.利用TG-DTA、XRD、TEM、BET、UV-Vis、HPLC等测试手段对制备过程、样品的结构和性能进行了研究,探讨了明胶浓度、煅烧温度对产物粒径和光催化活性的影响.结果表明:利用凝胶网格控制合成法不仅能够控制纳米微粒的形状和大小,而且可防止沉淀物相互聚集和团聚.以染料罗丹明B溶液为目标降解物,1 h的降解率为99.9%,最佳光催化剂的合成条件:13%明胶浓度、350℃煅烧2 h.     

ZnO纳米颗粒锚定的亚微米碳纤维的制备及其吸波性能

使用静电纺丝技术结合水热法制备了表面锚定ZnO纳米颗粒的亚微米碳纤维（ZnO/SDCFs）复合物,并详细研究了反应溶液的pH值对复合物的结构、组成、电磁特性和吸波性能的影响。结果显示,随着pH值的升高,ZnO的含量增加,介电常数、介电损耗以及电磁衰减能力均下降,但阻抗匹配程度提高。相比于纯碳纤维,所有ZnO/SDCFs复合物的吸波性能均得到不同程度的加强。其中,pH值等于8时所制备的ZnO/SDCFs-8复合物拥有最好的吸波性能,主要归因于电磁衰减能力和阻抗匹配间的更好平衡。当ZnO/SDCFs-8的填充量仅为2.5%（质量分数）、厚度为1.7 mm时,相应吸波涂层的最小反射损耗达到-44.1 dB,低于-10 dB的有效吸收带宽为6.1 GHz,频率范围为11.9~18 GHz;当厚度为3.0 mm时,有效吸收带宽可提高到11.8 GHz（6.2~18 GHz）。     

Green Synthesis,Characterization, and Antibacterial Properties of Silver Nanoparticles Obtained by Using Diverse Varieties of Cannabis sativa Leaf Extracts

Cannabis sativa L. (hemp) is a plant used in the textile industry and green building material industry, as well as for the phytoremediation of soil, medical treatments, and supplementary food products. The synergistic effect of terpenes, flavonoids, and cannabinoids in hemp extracts may mediate the biogenic synthesis of metal nanoparticles. In this study, the chemical composition of aqueous leaf extracts of three varieties of Romanian hemp (two monoecious, and one dioecious) have been determined by Fourier-Transformed Infrared spectroscopy (FT-IR), high-performance liquid chromatography, and mass spectrometry (UHPLC-DAD-MS). Then, their capability to mediate the green synthesis of silver nanoparticles (AgNPs) and their pottential antibacterial applications were evaluated. The average antioxidant capacity of the extracts had 18.4 ± 3.9% inhibition determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH^•) and 78.2 ± 4.1% determined by 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS™) assays. The total polyphenolic content of the extracts was 1642 ± 32 mg gallic acid equivalent (GAE) L⁻¹. After this, these extracts were reacted with an aqueous solution of AgNO₃ resulting in AgNPs, which were characterized by UV−VIS spectroscopy, FT-IR, scanning electron microscopy (SEM-EDX), and dynamic light scattering (DLS). The results demonstrated obtaining spherical, stable AgNPs with a diameter of less than 69 nm and an absorbance peak at 435 nm. The mixture of extracts and AgNPs showed a superior antioxidant capacity of 2.3 ± 0.4% inhibition determined by the DPPH^• assay, 88.5 ± 0.9% inhibition as determined by the ABTS^•+ assay, and a good antibacterial activity against several human pathogens: Escherichia coli, Klebsiella pneumoniae, Pseudomonas fluorescens, and Staphylococcus aureus.     

Green Synthesis of Zinc Oxide Nanoparticles Using Pomegranate Fruit Peel and Solid Coffee Grounds vs. Chemical Method of Synthesis,with Their Biocompatibility and Antibacterial Properties Investigation

This research aims to investigate the synthesis, characterization, and evaluation of the biocompatibility and antibacterial activity of novel zinc oxide (ZnO) nanoparticles (NPs) prepared by Punica granatum peel and coffee ground extracts as the reducing and capping agents. Chemically synthesized ZnONPs were prepared using zinc acetate dihydrate and sodium hydroxide as reducing precursors. ZnONPs were characterized using an ultraviolet-visible spectrophotometer (UV-VIS), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and Fourier transform infrared (FTIR) spectroscopy. Peaks of UV spectra were 300 nm for ZnONPs_PPE, 320 nm (ZnONPs_CE), 290 nm, and 440 nm (ZnONP_Chem), thereby confirming ZnONPs formation. The X-ray diffractograms revealed their hexagonal structure. TEM micrographs of the biosynthesized ZnONPs revealed their hexagonal pattern and nanorod shape for ZnONPs_Chem with particle sizes of 118.6 nm, 115.7 nm, and 111.2 nm, respectively. The FTIR analysis demonstrated the presence of proteins, carboxyl, and hydroxyl groups on ZnONPs surfaces that act as reducing and stabilizing agents. ZnONP_Chem shows the antibacterial effect on Staphylococcus aureus, Enterobacter aerogenes, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Punica peel and coffee ground extracts are effective reducing agents for green ZnONPs synthesis with a lower cytotoxic effect on Vero cells than ZnONPs_Chem with IC50 = 111, 103, and 93 μg/mL, respectively.     

ZnO Nanoparticles Obtained by Green Synthesis as an Alternative to Improve the Germination Characteristics of L. esculentum

Tomato is an important crop due to its nutritional contributions and organoleptic properties, which make it an appetizing vegetable around the world. In its sowing, the use of seed is the most accessible propagation mechanism for farmers. However, the induction to germination and emergence is often limited in the absence of stimulants that promote the development and growth of the seedling, added to the interference of infectious agents that notoriously reduce the vitality and viability of the seed. Given this, it was proposed as a research objective to determine the effect of zinc oxide nanoparticles (ZnO NPs) mediated by a green route on the germinative characteristics of Lycopersicon esculentum Mill. 1768 “tomato”. The experimental phase consisted of the synthesis of ZnO NPs and its subsequent characterization. After its synthesis, its inoculation was conducted during the germination of seeds of L. esculentum, considering six sample groups for the treatment with zinc nanoparticles (T1: Control; T2: 21.31 ppm; T3: 33.58 ppm; T4: 49.15 ppm; T5: 63.59 and T6: 99.076 ppm). The results indicate that concentrations close to 100 ppm of ZnO NPs are ideal in the treatment of L. esculentum seeds, due to the promotion of enzymatic and metabolic activity to achieve cell elongation; likewise, the biosynthesized nanoparticles showed no phytotoxicity, due to the fact that, in all the treatments, there were processes of germination and emergence. This was linked to the generation of a Zn⁰-phenolate complex through a chelating effect, which generates compatibility with the seed and, compared to classic inorganic synthesis, usually shows phytotoxicity. In this sense, green synthesis is presented as a great alternative in this type of application.     

不同形貌氧化锌的微波水热法制备及其光催化性能

采用微波水热法在乙二醇的辅助下,制备出一系列不同形貌的氧化锌(Zn O)纳米/微米颗粒。扫描电子显微镜测试结果表明,乙二醇的加入量对样品的形貌有着非常显著的影响,通过控制乙二醇的加入量,可以得到不规则片状、六方棱柱孪晶、梭子形和球形等形貌的Zn O纳米/微米颗粒。从微波反应器检测压力结果可以看出,乙二醇的加入量对反应体系的压力影响非常显著,这起到了调控纳米晶生长速度的效果进而得到不同形貌的样品。在此基础上,系统测试了样品在氙灯照射下光催化降解罗丹明B的能力,结果表明,乙二醇加入量大于12 m L时的球状样品光催化效率要远高于其他样品,在50 min内能完成对罗丹明B的降解。     

Sustainable–Green Synthesis of Silver Nanoparticles Using Aqueous Hyssopus officinalis and Calendula officinalis Extracts and Their Antioxidant and Antibacterial Activities

Silver nanoparticles (AgNPs) biosynthesized using aqueous medical plant extracts as reducing and capping agents show multiple applicability for bacterial problems. The aim of this study was to expand the boundaries on AgNPs using a novel, low-toxicity, and cost-effective alternative and green approach to the biosynthesis of metallic NPs using Calendula officinalis (Calendula) and Hyssopus officinalis (Hyssopus) aqueous extracts. The formation of AgNPs was confirmed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) techniques. The effectiveness of biosynthesized AgNPs in quenching free radicals and inhibiting the growth of Gram-positive and Gram-negative microorganisms was supported by in vitro antioxidant activity assay methods and using the Kirby–Bauer disk diffusion susceptibility test, respectively. The elucidated antimicrobial and antioxidative activities of medical plant extracts were compared with data from the engineered biosynthetic AgNPs. The antimicrobial effect of engineered AgNPs against selected test cultures was found to be substantially stronger than for plant extracts used for their synthesis. The analysis of AgNPs by TEM revealed the presence of spherical-shaped nano-objects. The size distribution of AgNPs was found to be plant-type-dependent. The smaller AgNPs were obtained with Hyssopus extract (with a size range of 16.8 ± 5.8 nm compared to 35.7 ± 4.8 nm from Calendula AgNPs). The AgNPs’ presumably inherited biological functions of Hyssopus and Calendula medical plants can provide a platform to combat pathogenic bacteria in the era of multi-drug resistance.     

Antibacterial Activity of Biosynthesized Selenium Nanoparticles Using Extracts of Calendula officinalis against Potentially Clinical Bacterial Strains

The use of selenium nanoparticles (SeNPs) in the biomedical area has been increasing as an alternative to the growing bacterial resistance to antibiotics. In this research, SeNPs were synthesized by green synthesis using ascorbic acid (AsAc) as a reducing agent and methanolic extract of Calendula officinalis L. flowers as a stabilizer. Characterization of SeNPs was performed by UV-vis spectrophotometry, infrared spectrophotometry (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) techniques. SeNPs of 40–60 nm and spherical morphologies were obtained. The antibacterial activity of marigold extracts and fractions was evaluated by disk diffusion methodology. The evaluation of SeNPs at different incubation times was performed through the colony-forming unit (CFU) count, in both cases against Serratia marcescens, Enterobacter cloacae, and Alcaligenes faecalis bacteria. Partial antibacterial activity was observed with methanolic extracts of marigold leaves and flowers and total inhibition with SeNPs from 2 h for S. marcescens, 1 h for E. cloacae, and 30 min for A. faecalis. In addition, SeNPs were found to exhibit antioxidant activity. The results indicate that SeNPs present a potentiated effect of both antimicrobial and antioxidant activity compared to the individual use of marigold extracts or sodium selenite (Na₂SeO₃). Their application emerges as an alternative for the control of clinical pathogens.     

Green Synthesis of ZnO Nanoparticles Using Plant Extract as a Template

Plant-based nanoparticles (NPs) have found great interest among various scientist in the present era and used in various sector including medicine, agriculture, and food industry. The various chemical constituents of plants aid in the bioreduction of metal ions to a nanoscale. Among the various NPs synthesized, zinc oxide (ZnO) NPs hold a premier position. ZnO NPs have use in textile, cosmetic, diagnostics, optoelectronics, photocatalysis, diodes, and many other areas. NPs synthesized through green synthesis have a potentially greater role in treating clinical pathogens. Present investigations show a simple eco-friendly method for the synthesis of ZnO NPs from the husk of sunflower seeds. Sunflower is an economically important crop, for the formation of edible oil. The husk is considered to be a waste, product in oil industry, however, the biomolecules present in sunflower husk can be used to produce ZnO NPs. Present investigations reveal formation of ZnO NPs and investigations of their structure through scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. Their optical properties have been studied by ultraviolet–visible spectrophotometer (UV–Vis) and fluorophotometer. ZnO NPs have also been investigated for their potential phytoremedial properties.     

Sunlight Photocatalytic Performance of ZnO Nanoparticles Synthesized by Green Chemistry Using Different Botanical Extracts and Zinc Acetate as a Precursor

In this work, the assessment of Azadirachta indica, Tagetes erecta, Chrysanthemum morifolium, and Lentinula edodes extracts as catalysts for the green synthesis of zinc oxide nanoparticles (ZnO NPs) was performed. The photocatalytic properties of ZnO NPs were investigated by the photodegradation of methylene blue (MB) dye under sunlight irradiation. UV-visible (UV-Vis) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Thermogravimetric (TGA), and Brunauer-Emmett-Teller analysis (BET) were used for the characterization of samples. The XRD results indicate that all synthesized nanoparticles have a hexagonal wurtzite crystalline structure, which was confirmed by TEM. Further, TEM analysis proved the formation of spherical and hemispherical nanoparticles of ZnO with a size in the range of 14–32 nm, which were found in aggregate shape; such a size was well below the size of the particles synthesized with no extract (~43 nm). ZnO NPs produced with Tagetes erecta and Lentinula edodes showed the best photocatalytic activity, matching with the maximum adsorbed MB molecules (45.41 and 58.73%, respectively). MB was completely degraded in 45 min using Tagetes erecta and 120 min using Lentinula edodes when subjected to solar irradiation.     

Local Structure of ZnO Micro Flowers and Nanoparticles Obtained by Micro‐Segmented Flow Synthesis

The micro‐segmented flow technique was applied for continuous synthesis of ZnO micro‐ and nanoparticles with short residence times of 9.4 s and 21.4 s, respectively. The obtained particles were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Small angle X‐ray scattering (SAXS) and photoluminescence spectroscopy were used to determine the size and optical properties of ZnO nanoparticles. In addition, extended X‐ray absorption fine structure (EXAFS) spectroscopy was employed to investigate local structural properties. The EXAFS measurements reveal a larger degree of structural disorder in the nanoparticles than the microparticles. These structural changes should be taken into consideration while evaluating the size‐dependent visible emission of ZnO nanoparticles.     

Green Synthesized ZnO Nanoparticles as Biodiesel Blends and Their Effect on the Performance and Emission of Greenhouse Gases

Pollution and global warming are a few of the many reasons for environmental problems, due to industrial wastes and greenhouse gases, hence there are efforts to bring down such emissions to reduce pollution and combat global warming. In the present study, zinc oxide nanoparticles are green synthesized using cow dung as fuel, through combustion. Synthesized material was characterized by FTIR, XRD, UV, and FESEM. The as-prepared ZnO-GS NPs were employed as a transesterification catalyst for the preparation of biodiesel from discarded cooking oil. The biodiesel obtained is termed D-COME (discarded cooking oil methyl ester), which is blended with 20% commercial diesel (B20). Additionally, this blend, i.e., B20, is further blended with varying amounts of as-prepared ZnO-GS NPs, in order to ascertain its effects on the quality of emissions of various greenhouse gases such as hydrocarbons, CO_x, NO_x. Moreover, the brake thermal efficiency (BTHE) and brake specific fuel consumption (BSFC) were studied for their blends. The blend (B20) with 30 mg of ZnO-GS, i.e., B20-30, displays the best performance and reduced emissions. Comparative studies revealed that the ZnO-GS NPs are as efficient as the ZnO-C NPs, indicating that the green synthetic approach employed does not affect the efficiency of the ZnO NPs.     

ZnO纳米粒子的表面光电压谱和光催化性能

采用焙烧前驱物碱式碳酸锌的方法制备了不同粒径的ZnO纳米粒子，而用粒径 最小的作为光催化剂，通过光还原过程分别得了贵金属质量分数为0.5%和0.75%的 Pd/ZnO或Ag/ZnO复合纳米粒子。利用XRD，TEM，XPS，SPS和EFISPS等测试技术对样 品进行了表征，并通过光催化氧化气相正庚烷评估了样品的光催化活性，考察了微 晶尺寸和贵金属Pd或Ag的沉积对ZnO纳米粒子表面光电压信号以及光催化活性的影 响，探讨了样品表面光电压谱与其光催化活性的关系，说明了可以通过表面光电压 谱的测试来初步地评估纳米粒子的光催化活性。结果表明：随着ZnO纳米微晶尺寸 的减小，其SPS信号强度逐渐变弱，而光催化活性逐渐升高；沉积适量的贵金属Pd 或Ag后，ZnO纳米粒子的SPS信号强度明显下降，而其光催化活性却有所升高。此外 ，对ZnO纳米粒子光催化剂的失活机理进行了分析。     

Multifunctional Eco-Friendly Synthesis of ZnO Nanoparticles in Biomedical Applications

This work describes an environmental-friendly preparation of ZnO nanoparticles using aqueous oat extract. The advanced electrochemical and optical features of green synthesized ZnONPs displayed excellent antibacterial activity and exhibited an important role in pharmaceutical determinations. The formation of nanoscale ZnO was confirmed using various spectroscopic and microscopic investigations. The formed nanoparticles were found to be around 100 nm. The as-prepared ZnONPs were monitored for their antibacterial potential against different bacterial strains. The inhibition zones for ZnONPs were found as Escherichia coli (16 mm), Pseudomonas aeruginosa (17 mm), Staphylococcus aureus (12 mm) and Bacillus subtilis (11 mm) using a 30-µg mL⁻¹ sample concentration. In addition, ZnONPs exhibited significant antioxidant effects, from 58 to 67%, with an average IC₅₀ value of 0.88 ± 0.03 scavenging activity and from 53 to 71% (IC₅₀ value of 0.73 ± 0.05) versus the scavenging free radicals DPPH and ABTS, respectively. The photocatalytic potential of ZnONPs for Rhodamine B dye degradation under UV irradiation was calculated. The photodegradation process was carried out as a function of time-dependent and complete degradation (nearly 98%), with color removal after 120 min. Conclusively, the synthesized ZnONPs using oat biomass might provide a great promise in the future for biomedical applications.     

Photochemical Synthesis,Spectral-Optical and Electrophysical Properties of Composite Nanoparticles of ZnO/Ag

The photochemical synthesis of nanoparticles of ZnO/Ag in isopropanol solutions has been carried out. Their optical properties have been studied and the parameters of the plasma resonance of the nanoparticles of silver in the ZnO/Ag composites have been calculated. It has been established that the hypsochromic shift of the plasma band of silver observed on irradiation of the nanocomposite is a result of accumulation of excess electrons on the ZnO/Ag particles which leads to equalization of the potentials of the conductions zones of the semiconductor and the metallic components of the nanocomposite.     

纳米金属铜与纳米氧化锌之间相互作用的EPR和XPS研究

由于纳米材料独特的表面效应、电子效应及量子尺寸效应 ,已被广泛应用于各个领域 .有关纳米材料研究的报道很多 [1～ 7] ,大部分是关于纳米材料的制备[1～ 4 ] 及其特性研究 .对于纳米金属及纳米氧化物之间相互作用的研究迄今尚未见报道 .本文采用超声分散和机械研磨法物理混合纳米金属铜粉和纳米氧化锌 ,借助 EPR和 XPS技术对样品进行了表征 ,发现混合体系出现了 Cu2 + 的顺磁信号 ,Zn L3M4 5M4 5俄歇动能和 O1s的电子结合能亦发生了变化 ,表明纳米 Cu0 和纳米 Zn O之间存在相互作用 ,作用形式为 Cu— O—Zn.1　实验部分1 .1　样品…     

纳米ZnO的制备及其光催化性能研究

本文以羟丙基纤维素(HPC)作为分散剂,运用沉淀法制备出了粒径均匀的ZnO颗粒.通过透射电子显微镜(TEM),X射线衍射(XRD),紫外可见光吸收光谱,光致发光谱(PL)对ZnO进行了性能表征,并探讨了其形成机理及制备中的影响因素.利用纳米ZnO作为光催化剂对有机染料罗丹明B进行了光降解实验,实验结果表明,此方法制备的ZnO具有良好的光催化性能,有望在治理环境污染等领域具有良好的应用.     

纳米氧化锌的机械力化学表面改性

采用机械力化学表面改性工艺,以硬脂酸为改性剂,在气流粉碎机中对纳米氧化锌进行解团聚和表面改性,并借助SEM、XRD、FF—IR和XPS对改性前后的氧化锌粉体进行结构表征．结果表明：硬脂酸分子化学键合在氧化锌表面．改性前后氧化锌的晶体结构相同,其颗粒的团聚性降低,二次粒径明显减小．通过测定改性样品的活化指数和亲油化度,选择最佳的改性剂用量为氧化锌质量的10％,氧化锌表面亲油疏水,在有机溶剂中有较好的分散性．     

Growth Dynamics Study of Silver Nanoparticles Obtained by Green Synthesis using Salvia officinalis Extract

ABSTRACT

Silver nanoparticles were synthesized by the bottom-up approach using Salvia officinalis extract, and their growth process was correlated with changes in their ultraviolet–visible spectra. Experiments were performed at different initial mixing ratios of silver nitrate to plant extract and at pH values to outline a pattern concerning the growth of silver nanoparticles obtained by this synthesis procedure. Relative areas calculated from the spectra from 350 to 600?nm were used as a comparison for the growth dynamics of silver nanoparticles synthesized in mixtures with different compositions. The graphical representation of relative areas vs. time presents four stages of nanoparticle growth with each linear portion corresponding to a different process rate.     

复合Ag/ZnO分级结构微球的制备及其光催化性能研究

采用化学沉淀法制备ZnO微球,利用柠檬酸三钠（TCD）避光还原硝酸银在ZnO表面沉积银粒子制备Ag/ZnO复合材料.利用XRD、SEM、TEM、EDS、FTIR、UV-vis DRS、PL、BET等对Ag/ZnO的结构、组分、形貌及光谱性质进行了表征,通过紫外及可见光照降解甲基橙溶液评价样品的光催化性能.结果表明：ZnO纳米微球是由ZnO纳米片相互交错构筑而成的具有丰富孔道的分级结构,Ag纳米粒子均匀沉积在ZnO纳米片上.Ag的沉积显著增加了ZnO的可见光吸收,猝灭了ZnO荧光,提高了ZnO催化活性.