JOURNAL OF NANOSTRUCTURE IN CHEMISTRY
Year:2018 | Volume:8 | Issue:3|Papers Count:9

Green chemistry approaches for the synthesis of metallic nanoparticles have become a new and promising field of research in recent years. Synthesis of metal nanoparticles [like gold (Au), silver (Ag), lead (Pb), platinum (Pt), copper (Cu), iron (Fe), cadmium (Cd), and other metal oxides such as titanium oxide (TiO), zinc oxide (ZnO), etc. ] by various chemical and physical approaches as well as the biological approaches mediated by number of microorganisms have been actively found. Plant-mediated synthesis approaches are found to be more reliable and economic route to synthesize these metal nanoparticles. Owing to the biodiversity of plant biomasses, the actual mechanism by which the plant constituents have contributed to the synthetic process is yet to be fully known. Although the feasibility of controlling, the size and shape of nanoparticles by variation in reaction conditions have been demonstrated in many studies. Conventionally, nanoparticles are synthesized by chemicals and physicochemical methods using several chemicals which later on become accountable for various risk due to their general toxicity, so that solving the objective biological approaches is coming up to fill these gaps. The plant-mediated synthesis process undergoes highly controlled approaches for making them suitable for metal nanoparticle synthesis. In addition, biological synthesis of metallic nanoparticles is inexpensive, one-step, and eco-friendly method. In addition, the plant-mediated nanoparticles are used as potential pharmaceutical agents for various diseases such as malaria, HIV, cancer, hepatitis, and other diseases. Including this some other relevant information regarding nanopharmaceutical products, companies that are involve in the manufacturing and commercialization process and their clinical trial status are also discussed. This review article gives an overview of the plant-mediated synthesis of metal nanoparticles, possible compounds, and mechanisms that might be responsible for the reduction process as well as the potential pharmacological applications, currently available nanopharmaceutical products and their marketing status.

The nanostructured materials offer various advantages as they provide more flexible space for ease reconstruction, as their nanosize expands the limits and results in confinement effect, enhanced mechanical stability, and large surface area, and make them suitable for photocatalytic activities. The advancement in synthesis techniques provides the freedom to alter its physical properties as per the demand. This article provides a 360° view point on the nanomaterials which are used for solar energy harnessing with respect to environmental and energy application. The discussion emphasizes on various synthesis methods of nanostructured materials, their mechanistic features, usage in demanding applications such as photosplitting of water for hydrogen production, artificial photosynthesis, and water and wastewater treatment with an endnote highlighting the future scope of nanomaterials for real-world applications.

A facile, eco-friendly synthesis of zinc oxide nanoparticles (ZnO NPs) employing Bauhinia tomentosa leaf extract as bioreducing agent was reported. The green-synthesized ZnO NPs were characterized by UV– Vis, TEM, EDX, XRD, and FTIR analyses. The formation of ZnO NPs was confirmed by the appearance of characteristic SPR peak at 370 nm due to the collective oscillation of electrons in the conduction band in UV– Vis spectra. The hexagonal morphology exhibiting nanosized ZnO was observed from the TEM and XRD analyses. The chemical bonds present in the as-synthesized ZnO NPs were identified by FTIR analysis. ZnO NPs showed a significant antibacterial activity against Gram-negative bacteria P. aeruginosa and E. coli than Gram-positive bacteria. Results of this study demonstrated that B. tomentosa leaf extract containing phytochemicals such as alkaloids, terpenoids, flavonoids, tannins, carbohydrates, and sterols possess bioreducing property for ZnO synthesis and the obtained ZnO NPs could be employed effectively as a better bactericidal agent for biological applications.

Bacterial cellulose (BC) is a three-dimensional interconnected network of biosynthesized nanofibers. Its rehydration potential would be reduced significantly after its first drying, as a result of entanglement and jamming of cellulose polymer chains. Consequently, its versatility would be also reduced to some limited applications in which repeated water absorbance potential is not of great importance. This study aims to prevent the drawback of carboxylic bridging/cross-linking between cellulose polymer chains. Ten-day-cultured BC pellicles were immersed in various citric acid solutions (as bridging agent) and cured at 160 ° C for 5 min. The formation of bridges was confirmed using attenuated total reflection– fourier transform infrared spectroscopy. Scanning electron microscope images showed that there is a different porosity bridged/cross-linked BC specimens (XBC). According to Brunauer– Emmett– Teller analysis, the surface area of XBC (20 w/v % with catalyst) got 87. 5 times larger than that of the unbridged/pristine BC (PBC). X-ray diffraction patterns showed no change of crystallinity of XBC in comparison with PBS. The thickness and wettability of XBC samples were 137 and 3. 27 times more than PBC samples orderly. Furthermore, the water swelling rate increased significantly for XBC in comparison with PBC. Meanwhile, treated samples had lower elongation and strength than normal BC. The conclusion is that XBC could conserve its repeated absorbency potential after the presented process.

In the present study, the effect of calcination temperature on the structure and performance of mesoporous CaO/TiO2– ZrO2 catalyst fabricated by sol– gel method used in the esterification reaction was assessed. Then, CaO/TiO2 catalyst was also synthesized via the same method to evaluate the effect of zirconia cations on its properties and activity. The samples were characterized by X-ray Diffraction (XRD), Fourier transmittance infra-red (FT-IR), Brunauer– Emmett– Teller (BET)– Barrett-Joyner-Halenda (BJH), scanning electron microscope (SEM) and transmission electron microscopy (TEM) analyses. Moreover, Hammett indicator method was utilized to assess the acidity and basicity of the samples. It was found that zirconium was clearly incorporated in CaO/TiO2 lattice and transformed that from amorphous phase to crystalline structure. In addition, the basicity and acidity of CaO/TiO2 was clearly increased by zirconia loading. Evaluation of the samples’ activity presented that CaO/TiO2 catalyst exhibit no activity in the esterification reaction, while all CaO/TiO2– ZrO2 catalysts showed high ability to convert oleic acid to its ester. Moreover, the catalyst calcined at 400 ° C showed the highest activity in the esterification reaction with desirable properties such as high crystallinity, acidity, basicity and surface area along with well-distribution of particle size and pore size. The best catalyst converted around 90% of oleic acid to ester at optimized conditions of 150 ° C, 12: 1 molar ratio of methanol/oleic acid, 3 wt% of catalyst for 4 h of reaction time. Moreover, the sample was successfully used for five runs without significant reduction in activity that makes it a suitable choice as a catalyst for industrial applications.

Green synthesis of metallic nanoparticles by means of renewable bioresources has emerged as a new trend in current nanotechnology research with improved environmental safety. In the current study, monodispersed gold nanoparticles (AuNPs) with excellent stability were prepared in a completely green and cost effective manner using aqueous extract of marine macroalgae-Padina tetrastromatica. The influence of reaction conditions such as the quantity of seaweed extract, temperature, precursor metal ion concentration, reaction time and pH on the biosynthesis of nanoparticle was evaluated spectroscopically and also with the help of high resolution transmission electron microscopy (HR-TEM). These physicochemical parameters not only affected the rate of formation but also the size and morphology of resultant nanoparticles. Optimum conditions resulted in the generation of nearly spherical AuNPs having an average particle size of 11. 4 nm. The high crystallinity of the biogenic AuNPs was confirmed from characteristic diffraction peaks in XRD profile, clear lattice fringes in the HR-TEM image and bright circular spots in the SAED pattern. The presence of metallic gold was evidenced from EDAX profile. FTIR study revealed the role of secondary metabolites in the bioreduction as well as stabilization of AuNPs. The study also highlights the spectroscopic investigation on the catalytic efficacy of the biosynthesized AuNPs in the reduction reactions of hazardous organic dyes, eosin yellow and Congo red using sodium borohydride, which have a pseudo-first order kinetics. Thus, the biosynthesized metal nanoparticles using renewable marine resources like seaweeds act as promising materials for the application in environmental protection.

Super-paramagnetic iron-oxide nanoparticles (SPIONs) have been exploited from a very long time and are researched profoundly due to their unique properties. In this study, SPIONs were synthesized using environmentally accepted green synthesis process where Azadirachta indica leaf extract was used as one of the reducing agents along with basic metal precursors used in chemical processes. The synthesized SPIONs were characterised using microscopic analysis (SEM, TEM, and AFM), spectroscopic analysis (FT-IR, UV– Vis, XRD, Raman, and zeta potential), and magnetometry (SQUID). The SPIONs were then tested for its application in the removal of heavy metals from tannery waste water and also X-ray imaging.

In this project, facile, rapid biosynthesis and characterization of silver– montmorillonite (MMT) nanocomposite is carried out at ambient temperature. Silver nanoparticles (Ag-NPs) were prepared by water extract of the plant [Satureja hortensis (L)] as the reducing agent and MMT as interlamellar space for controlling the size of Ag-NPs. MMT was sonicated in the aqueous AgNO3 solution and Ag+ ions were reduced to Ag° using water extract of Satureja hortensis (L). The nanocomposite was evaluated using ultraviolet– visible spectroscopy (UV– Vis), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM study showed the formations of nanocomposite using water extract of Satureja hortensis L in the range of 4. 88– 26. 70 nm and an average particles size of 15. 79 nm. In addition, XRD studies indicated that the particles have a face centred cubic (FCC) structure. The nanocomposite showed antibacterial effects against bacteria.

The present study demonstrated the simple, cheap, eco-friendly synthesis of the silver nanoparticles (S-AgNPs) using Symphytum officinale leaf extract. The biosynthesized S-AgNPs were characterized by UV– Vis, FE-TEM, elemental mapping, EDX, zeta potential, XRD, SAED, and FT-IR. The characterization results revealed the irregular shape and relatively stable nature of synthesized S-AgNPs. The average particle size was determined to be 87. 46 nm. The zeta potential shows the negative surface charge (− 25. 5 mV) of S-AgNPs. After characterization, we investigated the anti-aging effect of S-AgNPs in HaCaT keratinocyte cells. HaCaT keratinocyte cells were treated with S-AgNPs at concentrations 1, 10, 100 μ g mL− 1 after UVB or non-UVB irradiation. The S-AgNPs significantly inhibited the production of matrix metalloproteinase-1 and IL-6 but increased the expression of procollagen type 1. The data suggest that S-AgNPs have photoprotective properties and may have potential to be used as an agent against photoaging.