Volume 5, Issue 6 - Special issue: Green Nanotechnology

In vitro and in vivo experiments were conducted to evaluate the bioactivity of nanoparticles of silver and neem (AgNeemnano) solution on some organisms that cause yam rot. In the in vitro study, organisms were isolated from a decaying yam tuber and identified as Fusarium moniliforme and Lasiodiplodia theobromae. The organisms were cultured in Sabouraud dextrose agar. With a cork borer of diameter 8 mm, cups were made at the centre of each of the agar plates, and then 0.05 ml AgNeemnano solution in varying concentrations (28.40, 56.81, 113.63, and 227.27 mg/ml) was aseptically introduced into the cups starting from the lowest to the highest concentration. The plates were incubated at 35°C for 48 h, and the zones of inhibition were determined. In the in vivo study, sterile yam slices, each weighing approximately 12.6 g, were dipped into each level of AgNeemnano solution for 3 min and thereafter inserted into the Petri dishes containing each of the organisms. The minimum inhibition concentration (MIC) of the AgNeemnano that inhibited the mycelial growth of F. moniliforme was 0.8 mg/ml, while the MIC of the AgNeemnano for L. theobromae was 0.5 mg/ml. The sterile yam slices dipped in the AgNeemnano solution and later inserted into cultured organisms were not attacked by the rot-causing organisms.

In the present work, we report the phytosynthesis of AgNPs mediated by leaf and seed extracts of Synsepalum dulcificum . The extracts catalyzed the formation of brown colloidal AgNPs, which stabilized in 10 min. The leaf and seed AgNPs yielded surface plasmon resonance at 440 and 438.5 nm, respectively. Prominent peaks at 3408, 2357, 2089, and 1639 cm −1 were recorded for leaf AgNPs, whereas 3404, 2368, 2081, and 1641 cm −1 were revealed for seed-mediated AgNPs from Fourier transform infrared data. These showed the involvement of phenolic compounds and proteins in the phytosynthesis. The particles were fairly spherical and crystalline in nature having size of 4–26 nm, with prominence of silver in the colloidal solutions. The particles inhibited the growth of drug-resistant strains of Pseudomonas aeruginosa and Klebsiella granulomatis with zone of inhibition of 11–24 mm. Also, the phytosynthesized AgNPs completely inhibited the growth of Aspergillus flavus and Aspergillus niger . In addition, by using 20 μg/ml of AgNPs, malachite green was degraded by approximately 80% in 24 h. Similarly, the particles displayed blood anticoagulant activities as well as achieved thrombolysis. The AgNPs can be explored for biomedical and catalytic applications. The report is the first on the eco-friendly synthesis of nanoparticles by S. dulcificum.

The present report summarizes an eco-friendly approach for the biosynthesis of silver nanoparticles (AgNPs) using the leaf extract of lavender. Initially, the synthesis of AgNPs was visually observed by the appearance of a wine red color. The optical property, morphology, and structure of as-synthesized AgNPs were characterized by UV-visible spectroscopy, dynamic light scattering, transmission electron microscopy, and X-ray diffraction analyses. All characterization data revealed the formation of crystalline and spherical AgNPs (Ag/Ag 2 O) with size around 10–80 nm at λ max =440 nm. The surface-modified AgNPs showed an effective catalytic activity toward the reduction of 4-nitrophenol to 4-aminophenol, optical sensing of H 2 O 2 , and antioxidant activity against 1,1-diphenyl-2-picrylhydrazyl. The experimental approach is simple, facile, economical, and easily reproducible without any use of toxic chemicals, and opens up new scope for future biotechnology applications.

Here, we report on the novel green synthesis of metallic copper nanoparticles from copper sulfate solution by using the leaf extract of Heliconia psittacorum . The stability and gradual formation of copper nanoparticles during interaction with the extract were investigated using ultraviolet-visible spectroscopy. The pattern of X-ray diffraction revealed the crystallinity and different phases of the nanoparticles. High-resolution transmission electron microscopy was done to obtain information about the morphology and microstructure of the green nanoparticles. The infrared spectra detected organic bioactive molecules associated with capping and stabilization of the particle surface. The antibacterial properties of these bioengineered Cu nanoparticles were tested toward a Gram-positive bacteria – Staphylococcus aureus – and two strains of Gram-negative bacteria – Escherichia coli and Pseudomonas putida . The antibacterial study showed that these biogenic copper nanoparticles have potent bactericidal property toward the examined bacterial species.

Gold nanoparticles (AuNPs) were synthesized using edible mushroom Agaricus bisporus extract as both reducing and stabilizing agents via microwave irradiation method. The effects of the microwave exposure time and the amount of HAuCl 4 solution (1 m m ) on the mean particle size, concentration, and polydispersity index (PDI) of the synthesized AuNP solution were investigated using response surface methodology. Mushroom extract was characterized by Fourier transform infrared. The synthesized AuNPs were characterized by dynamic light scattering, UV-Vis spectroscopy, and transmission electron microscopy. Well-dispersed and spherical AuNPs with the minimum mean particle size and PDI, and maximum concentration and zeta potential of 33.56±1.8 nm, 0.855±0.02 ppm, 148.88±2.7 ppm, and +17.2 mV, respectively, were obtained using 2.62 ml of HAuCl 4 and 0.2 ml of mushroom extract for 55 s. The antibacterial activity of the fabricated AuNPs was assessed against both Gram-negative ( Escherichia coli ) and Gram-positive ( Staphylococcus aureus ) bacteria and was found to be possessing high bactericidal effects.

During the past few years, scientists have shown that climate change is a serious problem that mandates adequate solutions. Greenhouse gas emissions such as carbon dioxide contribute to heat trapping in the atmosphere, which increases the global temperature. Reducing greenhouse gas emissions and the carbon footprint to zero is an essential step toward maintaining a 2°C temperature change. In doing so, researchers and scientists have focused much attention on finding alternative technologies that provide clean and sustainable energy. In particular, nanotechnology can offer this alternative solution to the ongoing energy crisis. The recent progress in nanomaterial research has focused on the development of high-efficiency optoelectronics, batteries, low-power electronics, and thermoelectric devices for energy generation applications. With the emergence of new nanomaterials, such as carbonaceous materials and transition metal dichalcogenides, new physics have emerged. Scientists and engineers are still eager to answer some of the fundamental issues concerning these nanomaterials, including optical, electrical, and thermal properties. Yet, to this day, nanotechnology solutions to provide a sustainable energy are hinged by the ability to control and fully understand the properties of these nanomaterials. Here, we highlight some of the recent progress carried out in nano-optoelectronics, and share our thoughts on the opportunities and challenges facing low-dimensional devices to generate clean and sustainable energy.

The green synthesis of nanoparticles has received great attention in recent times owing to its advantages such as cost effectiveness, simplicity, eco-friendliness, biocompatibility, and wide applications over the conventional chemical and physical methods. Various kinds of biomolecules from microorganisms and plants have been successfully utilized for the synthesis of metallic and nonmetallic nanoparticles, and these have been well documented. However, the recent increase in the fabrication of metallic nanoparticles using agro-wastes, enzymes and microbial and plant-derived pigments and their respective areas of applications have not been compiled as a review article. Therefore, the present efforts have been aimed at compilation of reports on the use of these novel bio-resources for the green synthesis of nanoparticles. To the best of our knowledge, this is the first review article on the green synthesis of metallic nanoparticles using diverse agro-wastes, enzymes, and pigments of biological origin. It is envisaged that the compendium will bring to the fore the emerging importance of these bio-resources for nanobiotechnological applications.

Seaweed extracts are most studied recently for their ability to rapidly reduce metal ions than biomass such as bacteria, fungi, and plants. The reducing capacity of seaweeds depends on the presence of phytoconsitutents such as polysacchardies, phenolic compounds, proteins/enzymes, and other chelating agents. Marine seaweeds that belong to Chlorophyta, Rhodophyta, and Phaeophyta groups are reported to biosynthesize metal nanoparticles. The morphology and the stability of the nanoparticles obtained from seaweeds for biomedical and environmental applications are equivalent in most aspects to other “green” methodologies. The biosynthesis of nanoparticles using seaweeds can be scaled up to meet industrial requirements. Therefore, this review elaborates seaweeds as a better tool for the fabrication of metal nanoparticles.

Nanotechnology has remained relevant as a multifacet discipline, which cuts across different areas of science and technology. Several successful attempts had been documented regarding the involvement of biological materials in the green synthesis of various metal nanoparticles (MeNPs) because of their eco-friendliness, cost-effectiveness, safe handling, and ultimately less toxicity as opposed to the physical and chemical methods with their concomitant problems. Biological agents, including bacteria, fungi, algae, enzymes, plants, and their extracts, have been implicated in most cases by several authors. Moreover, nanotechnology in recent times has also made an inroad for animal species, specifically arthropods and metabolites thereof to be used as excellent candidates for the green synthesis of MeNPs. The increasing literature on the use of metabolites of arthropods for the green synthesis of nanoparticles has necessitated the need to document a review on their relevance in nanobiotechnology. The review, which represents the first of its kind, seeks to underscore the importance of arthropods in the multidisciplinary subject of nanoscience and nanotechnology.