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Polymeric coatings have been widely selected for the corrosion resistance of metallic surfaces. Both the conducting and non-conducting polymers have been applied for corrosion confrontation. The conducting polymers usually possess high electrical conductivity and corrosion resistance features. On the other hand, non-conducting hydrophobic polymers have also been used to avert the metal erosion. To improve the corrosion inhibition performance of the polymer coatings, nanocarbon nanofillers have been used as reinforcement. Graphene, especially, has gained an important position in the research on the corrosion-protecting nanocomposite coatings. Here, graphene dispersion and matrix–nanofiller interactions may significantly improve the anti-corrosion performance to protect the underlying metals. The graphene nanofiller may form an interconnecting percolation network in the polymers to support their electrical conductivity and thus their corrosion confrontation characteristics. Further research on the polymer/graphene nanocomposite and its anti-corrosion mechanism may lead to great advancements in this field.

This review article highlights essential manufacturing strategies for the formation of graphene reinforced polymeric nanocomposites. For graphene reinforced thermoplastic, thermosetting and conducting matrix nanomaterials have been manufactured using solution casting, melt blending, in situ polymerization, electrospinning, 3D printing, and several other techniques. Solution processing has been well thought-out as an advantageous technique, relative to melt mixing, in terms of graphene dispersion in polymeric matrices. An in situ polymerization process has also been considered valuable to form homogeneously dispersed polymer/graphene nanocomposites having superior physical characteristics. Nevertheless, the manufacturing techniques for polymer/graphene nanocomposites have relative advantages and disadvantages to be considered for graphene-based nanocomposites. Moreover, numerous challenges need to be overcome to optimize the processing parameters for the fabrication of high-performance polymer/graphene nanocomposites.

This study focuses on computational studies of chemical reactivity descriptors of some proposed drugs for COVID-19. Density functional theory calculations were used to optimize the structure and investigate the frontier orbitals and the chemical reactivity descriptors of these drugs. The frontier orbitals, which include both the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), play an essential role in molecular interactions and chemical reactivity of molecule. Polarizability, which determines the response of the susceptibility of a molecule to an approaching charge, is higher in the more complex drugs such as Hydroxychloroquine, Remdesivir, and Ivermectin compare to the smaller drugs. The HOMO and LUMO orbital energies were calculated to obtain the energy gap of the studied drugs, which is in the following order: Favipiravir Graphical abstract

The importance of green process in the synthesis of nanomaterials becomes universally known. In this study, we report on the efficiency of a Aspalathus linearis’s plant extract known as Rooibos tea on the synthesis of graphene via a bio-active process. Using several nanocharcterization techniques, our investigations on the main physico-chemical properties confirmed the ability of this plant extract as a reducing and capping agent on the synthesis of good quality few layered graphene sheets compared to several natural extracts and chemical agents. Furthermore, this eco-friendly cost-effective process allows the control and modulation of the optical and electrical properties of the prepared graphene. Moreover, this material was positively tested as silver NPs fluorescence quencher. Hence, Rooibos shows its ability as an effective chelating agent in the production of graphene sheets which serves electronic and optoelectronic related quenching applications.

Hyphaene thebaica fruits were used for the fabrication of spherical erbium oxide nanoparticles (HT-Er2O3 NPS) using a one-step simple bioreduction process. XRD pattern revealed a highly crystalline and pure phase with crystallite size of ~ 7.5 nm, whereas, the W–H plot revealed crystallite size of 11 nm. FTIR spectra revealed characteristic Er-O atomic vibrations in the fingerprint region. Bandgap was obtained as 5.25 eV using K-M function. The physicochemical and morphological nature was established using Raman spectroscopy, reflectance spectroscopy, SAED and HR-TEM. HT-Er2O3 NPS were further evaluated for antidiabetic potential in mice using in-vivo and in-vitro bioassays. The synthesized HT-Er2O3 NPS were screened for in vitro anti-diabetic potentials against α-glucosidase enzyme and α-amylase enzyme and their antioxidant potential was evaluated using DPPH free radical assay. A dose dependent inhibition was obtained against α-glucosidase (IC50 12 μg/mL) and α-amylase (IC50 78 μg/mL) while good DPPH free radical scavenging potential (IC50 78 μg mL−1) is reported. At 1000 μg/mL, the HT-Er2O3 NPS revealed 90.30% and 92.30% inhibition of α-amylase and α-glucosidase enzymes. HT-Er2O3 NPs treated groups were observed to have better glycemic control in diabetic animals (503.66 ± 5.92*** on day 0 and 185.66 ± 2.60*** on day 21) when compared with positive control glibenclamide treated group. Further, HT-Er2O3 NPS therapy for 21 days caused a considerable effect on serum total lipids, cholesterol, triglycerides, HDL and LDL as compared to untreated diabetic group. In conclusion, our preliminary findings on HT-Er2O3 NPS revealed considerable antidiabetic potential and thus can be an effective candidate for controlling the post-prandial hyperglycemia. However, further studies are encouraged especially taking into consideration the toxicity aspects of the nanomaterial.

Self-healing polymers and nanocomposites form an important class of responsive materials. These materials have the capability to reversibly heal their damage. For aerospace applications, thermosets and thermoplastic polymers have been reinforced with nanocarbon nanoparticles for self-healing of structural damage. This review comprehends the use of self-healing nanocomposites in the aerospace sector. The self-healing behavior of the nanocomposites depends on factors such as microphase separation, matrix–nanofiller interactions and inter-diffusion of polymer–nanofiller. Moreover, self-healing can be achieved through healing agents such as nanocapsules and nanocarbon nanoparticles. The mechanism of self-healing has been found to operate via physical or chemical interactions. Self-healing nanocomposites have been used to design structural components, panels, laminates, membranes, coatings, etc., to recover the damage to space materials. Future research must emphasize the design of new high-performance self-healing polymeric nanocomposites for aerospace structures.

This article presents a simple and low-cost green synthesized single-layer NiO selective solar absorber nanocoating prepared by spin coating on a Cu substrate at different rotational speeds (RS). The effects of substrate RS on the structural, morphological, chemical, and optical properties of the NiO nanocoatings were thoroughly investigated. The XRD results reveal the formation of pure diffraction peaks indexed to face-centered cubic NiO nanocoatings. SEM confirmed the uniform distribution of the NiO thin films with a nanosphere-like structure and the influence of RS variation on the formation of NiO nanostructures. EDS and XPS confirmed the presence of Ni and O in the green synthesized NiO coatings. AFM showed homogeneous nanopillar-like NiO thin films with the average surface roughness decreasing from 13.6 to 9.06 nm as the RS increased from 700 to 1300 RPM. Raman spectroscopy of the nanocoatings showed normal modes related to longitudinal optical and transverse optical phonons, and a combination of both, which implies the presence of a defect-rich or anti-ferromagnetically ordered NiO film responsible for the occurrence of more scattering peaks. UV–Vis–NIR and Fourier transform infrared spectroscopy (FTIR) were employed to characterize the optical properties of the nanocoatings. The green synthesized NiO nanocoatings deposited at 700 RPM exhibited excellent solar absorptance (α) of 0.92 and low thermal emittance (ɛ) of 0.11. The optical properties of the selective materials obtained in the present work were correlated with the non-stoichiometric nature of the spin-coated sample, multiple reflections, and interference-induced light absorption on the green synthesized surface. These results suggest that the NiO thin films prepared through this simple and environmentally benign green synthesis method can be promising candidates for efficient solar selective absorbers.

This research describes the use of surface-enhanced Raman spectroscopy (SERS) substrates based on colloidal silver nanoparticles (AgNPs) produced by laser ablation of silver granules in pure water that are inexpensive, easy to make, and chemically stable. Here, the effects of the laser power, pulse repetition frequency, and ablation duration on the Surface Plasmon Resonance peak of AgNPs solutions, were used to determine the optimal parameters. Also, the effects of the laser ablation time on both ablation efficiency and SERS enhancement were studied. The synthesized AgNPs were characterized by UV-Vis spectrophotometer and Raman spectrometer. The Surface Plasmon Resonance peak of AgNP solutions was centered at 404 nm confirming their synthesis. Using Raman spectroscopy, they had main bands centered at 196, 568, 824, 1060, 1312 cm-1, 1538 and 2350 cm-1. Their Raman spectral profiles remained constant within the first few days of storage at room temperature implying chemical stability. The Raman signals from blood were enhanced when mixed with AgNPs and this depended on colloidal AgNPs concentration. Using those generated by 12 hrs ablation time, an enhancement of 14.95 was achieved. Additionally, these substrates had an insignificant impact on the Raman profiles of samples of rat blood when mixed with them. The Raman peaks noted were 932, 1064, 1190, 1338, 1410, 1650 and 2122 cm-1. These SERS substrates can be applied to areas such as forensics, monitoring of the efficacy of drugs, disease diagnostics and pathogen detection. All this can be achieved by comparing the Raman spectra of the biological samples mixed with the synthesized SERS substrates for different samples. Thus, the results on the use of inexpensive, simple-to-prepare Raman substrates have the possibility of making surface-enhanced Raman spectroscopy available to laboratories with scarce resources in developing nations.

In this study, we theoretically investigate the response of a germanium thin film under femtosecond pulsed laser irradiation. Electron and lattice temperatures, as well as material-specific optical properties such as dielectric function and reflectivity, were calculated during the irradiation using an extended two-temperature model coupled with the carrier density rate equation and the Drude model. Melting and ablation fluence thresholds were also predicted, resulting in 0.14 J cm−2 and 0.35 J cm−2, respectively. An ultrafast change in both optical and thermal properties was detected upon laser irradiation. Results also indicate that thermal melting occurs after germanium takes on a metallic character during irradiation, and that the impact ionization process may have a critical role in the laser-induced thermal effect. Therefore, we suggest that the origin of the thermal modification of germanium surface under femtosecond laser irradiation is mostly due the impact ionization process and that its effect becomes more important when increasing the laser fluence.

Nanoparticles possess several properties, such as antimicrobial, anti-inflammatory, wound healing, catalytic, magnetic, optical, and electronic properties, that have allowed them to be used in different fields. Among them, zinc oxide (ZnO) has received copious consideration due to its technological and medicinal applications. Plant-mediated synthesis of ZnO nanoparticles has provided a cost-effective and eco-friendly method. Therefore, the objective of the study is to assess the effect of the precursor concentration and silver and cerium doping on the optical properties of ZnO nanoparticles synthesized via a green process using bush tea leaf extract as the chelating agent. Zinc nitrate hexahydrate was used as the precursor. Quasi-spherical-shaped ZnO nanoparticles were obtained with an average crystallite size ranging between 24.53 and 63.02 nm. The crystallite size was found to decrease with the increase of precursor concentration at 43.82 nm (0.05 g), 37.25 nm (0.10 g), 26.53 nm (0.50 g), and 24.53 nm (1 g); thereafter, the size increases with an increase in precursor concentration. The optimum precursor concentration was 1 g with the smallest grain size and a high purity level. The increase in annealing temperature induced an increase in the crystallite size of ZnO nanoparticles from 24.53 nm (600 °C) to 34.24 nm (800 °C), however, increasing the level of purity of the nanopowders. The band gap energies were 2.75 and 3.17 eV as calculated using the Tauc plot with variations due to the precursor concentrations. Doping with both silver and cerium increased the band gap of ZnO nanoparticles up to 3.19 eV and the increase in annealing temperature slightly augmented the band gap energy from 3.00 and 3.16 eV, respectively. Hence, doping with Ag and Ce induced the formation of nanorods at higher concentrations. This study successfully demonstrated that the natural plant extract of bush tea can be used in the bioreduction of zinc nitrate hexahydrate to prepare pure ZnO nanoparticles, thus extending the use of this plant to the nano producing industry.

Biosynthesis of silver nanoparticles (AgNPs) from marine actinobacteria offers a promising avenue for exploring bacterial extracts as reducing and stabilizing agents. We report extracellular extracts of Rhodococcus rhodochrous (MOSEL-ME29) and Streptomyces sp. (MOSEL-ME28), identified by 16S rRNA gene sequencing for synthesis of AgNPs. Ultrafine silver nanoparticles were biosynthesized using the extracts of R. rhodochrous and Streptomyces sp. and their possible therapeutic applications were studied. The physicochemical properties of nanoparticles were established by HR-SEM/TEM, SAED, UV–Vis, EDS, XRD, and FTIR. UV–Vis spectra displayed characteristic absorption at 430 nm and 412 nm for AgNPs from Streptomyces sp. (S-AgNPs) and Rhodococcus sp. (R-AgNPs), respectively. HR-SEM/TEM, XRD, EDS analysis confirmed the spherical shape, crystalline nature, and elemental formation of silver. Crystallite or grain size was deduced as 5.52 nm for R-AgNPs and 35 nm for S-AgNPs. Zeta-potential indicated electrostatic negative charge for AgNPs, while FTIR revealed the presence of diverse functional groups. Disc diffusion assay indicated the broad-spectrum antibacterial potential of S-AgNPs with the maximum inhibition of B. subtilis while R-AgNPs revealed potency against P. aeruginosa at 10 µg/mL concentration. Biogenic AgNPs revealed antileishmanial activity and the IC50 was calculated as 164 µg/mL and 184 µg/mL for R-AgNPs and S-AgNPs respectively. Similarly, the R-AgNPs and S-AgNPs revealed anti-cancer potential against HepG2 and the IC50 was calculated as 49 µg/mL and 69 µg/mL for R-AgNPs and S-AgNPs, respectively. Moreover, the antioxidant activity showed significant results. MTT assay on RD cells, L20B cells, and Hep-2C indicated intensification in viability by reducing the concentration of R-AgNPs and S-AgNPs. The R-AgNPs and S-AgNPs inhibited sabin-like poliovirus (1TCID50 infection in RD cells). Furthermore, hemocompatibility at low concentrations has been confirmed. Hence, it is concluded that biogenic-AgNPs has the potential to be used in diverse biological applications and that the marine actinobacteria are an excellent resource for fabrication of AgNPs.

We report a facile, green and precursor-based comparative study on the biosynthesis of zinc oxide (ZnO) nanoparticles (NPs) using anticancerous Fagonia indica as effective chelating agent. Biosynthesis was carried out using zinc sulfate and zinc acetate as precursor salts to make ZnOS and ZnOA NPs under similar experimental conditions which were characterized extensively for physical and biological properties. Scherrer equation deduced a mean crystallite size of ~23.4 nm for ZnOA NPs and ~41 nm for ZnOS NPs. The nature of the NPs was compared using UV, diffuse reflectance spectra, Fourier transform infrared spectroscopy, thermogravimetric analysis-DTA, selected area electron diffraction, EDS, zeta potential, high resolution (HR)-SEM, and HR-TEM. Detailed in vitro pharmacognostic activities revealed a significant therapeutic potential for ZnOA and ZnOS . Potential antimicrobial activities for the NPs and their nanocosmeceutical formulations are reported. ZnOA NPs were more cytotoxic to Leishmania tropica as compared to ZnOS . Significant antioxidant and protein kinase inhibition was obtained. The hemolytic assay indicated a hemocompatible nature of both ZnOA and ZnOS NPs. Catalytic degradation of crystal violet dye (CVD) by NPs was examined under different parameters (light, dark, UV). Furthermore, sonophotocatalytic degradation of CVD was also studied. Our results suggested that precursor can have a significant effect on the physical, biological, and catalytic properties of the NPs. In future, we recommend different other in vitro, in vivo biological activities, and mechanistic studies of these as-synthesized NPs.

The use of femtosecond laser to create sub-microscopic transient pores on the cell membrane allowing exogenous material into mammalian cells has become a very efficient optical delivery method over the past decade. This study focuses on laser-enabled delivery of antiretroviral (ARV) drugs into HIV-1 infected TZM-bl cells in vitro. A 1 kHz femtosecond laser emitting at a wavelength of 800 nm was used to photoporate cells at 6.5 μW. Trypan blue was used for characterisation and its uptake was quantified using Matlab software. Cell membrane damage was assessed using the lactate dehydrogenase (LDH) assay while HIV-1 infection was assessed using luciferase assay. Our results showed successful delivery of ARVs into HIV-1 infected cells without compromising their cell membranes, subsequently reducing the level of infection. The LDH assay showed no significant cell membrane damage of laser-treated cells, and the luciferase assay demonstrated significant reduction in the level of HIV-1 infection.

Hydrothermally synthesized electrodes of Co3O4@MnO2@NiO/GO were produced for use in supercapacitors. Graphene oxide (GO) was incorporated into the nanocomposites used for electrode synthesis due to its great surface area and electrical conductivity. The synergistic alliance among these composites and GO enhances electrode performance, life span, and stability. The structural properties obtained from the X-ray diffraction (XRD) results suggest that nanocomposites are crystalline in nature. The synergistic alliance among these composites and GO enhances electrode performance, life span, and stability. Performance assessment of these electrodes indicates that their characteristic performance was enhanced by C2+ radiation, with the uttermost performance witnessed for electrodes radiated with 5.0 × 1015 ions/cm2.

Raman spectroscopy (RS) is a modern scientific analytic fingerprint technique that detects, examines, and analyzes the constituent chemical composition of various substances (solid–liquid–gas and plasmons) through interaction of laser light with matter. It is intelligent to present qualitative and quantitative information about the sample’s chemical composition, polymorphism, phase, crystallinity, stress/strain, and contamination and impurity/defects. The key mechanism is profoundly based on the Raman principle that was originally named after and discovered by the Indian primer scientist C.V Raman, who won the Nobel prize after the exposure of the Raman effect [Raman 1916; Krishnan 1928]. This review briefly presents the physical origin of Raman scattering explaining the key classical and quantum mechanical concepts. Molecular variations of the Raman effect will also be considered, including resonance, coherent, and enhanced Raman scattering. Further, we discuss the molecular origins of prominent bands often found in the Raman spectra of SPR (surface plasmon resonance) samples. Finally, we examine the several active variations of Raman spectroscopy techniques in practice, looking at their applications, strengths, and challenges. This review is intended to be a starting resource for scientists new to Raman spectroscopy, providing theoretical background and practical examples as the foundation for further study and exploration of SPR and surface-enhanced Raman spectroscopy (SERS) techniques. While RS is now used in biology and medicine for novel pandemic diseases, Raman spectroscopy found its first applications in physics and chemistry and was mainly used to study vibrations and structure of molecules. One early factor limiting the implementation of RS was the weak scattering signal. Large intensities of monochromatic light are required to excite a detectable signal. This requirement became much easier to realize following the invention of the laser in 1960. Over the past decades, Raman spectroscopy has been prominently exploited better in biological applications, where it is able to detect and analyze DNA and RNA molecules. Generally, there are four main types of Raman spectroscopy, but the most feasible in biological field is the SERS. The noble metal nanoclusters play an important role for nanobiomedical and modern optical devices. The present review explored the single and bi-metallic (silver (Ag), copper (Cu), silver–copper (Ag–Cu), and copper–silver (Cu–Ag)) nanoclusters embedded in soda–lime glass that is prepared by ion-exchange method. The ion-exchanged glasses are annealed by different methods (furnace and laser). These samples exhibit surface plasmon and surface enhancement effect. Optical absorption spectroscopic analysis was done on the metal nanocluster composite glasses, and the spectra are well studied as a function of various post ion-exchange treatments and different sizes. As size effects are an essential aspect of nanomaterials, the effect of size on the optical absorption metal nanoclusters was studied using theoretical models and correlated with the experimental results. Formation of embedded bi-metallic nanoclusters is also achieved by furnace annealing or laser irradiation of the sequential Cu–Ag and Ag–Cu ion-exchanged samples. The formations of core–shell structures or alloying between the metal species were confirmed from the optical absorption spectra. This review analyzes the influence of different parameters (nanocluster size, morphology, and composition as well as surface plasmon resonance (SPR) wavelength) on SERS. Experimental study of SERS substrates consists of silver, copper, and alloyed copper–silver (Cu–Ag) or silver–copper (Ag–Cu) nanoclusters of various sizes and compositions with the aim of finding the optimal conditions for fabricating substrates with maximum SERS enhancement factors. The primary aim of this work is focused on the development of novel SERS-active substrates and their applications in various research fields. The basic principle is borrowing the rough feature from the supported under layer to produce the rough noble meal surface and achieve the surface enhancement effect. The prepared substrates meet the following requirements, such as stable, reproducible, possessing large enhancement factor, and easiness for preparation. SERS opens up exciting opportunities in the field of biophysical and biomedical spectroscopy, where it provides ultrasensitive detection and characterization of biophysically/biomedically relevant molecules and processes as well as a vibrational spectroscopy with extremely high spatial resolution. This review explains many fundamental features of SERS and then describes the use of embedded nanocluster for the fabrication of highly reproducible and robust SERS substrates. The present review discusses the synthesis of single and bi-metallic nanocomposite glasses by the commercial ion-exchange technique followed by the suitable thermal treatments like furnace and laser annealing. Post treatment, the samples were subjected to various studies like optical absorption and SERS, FESEM, photoluminescence, and grazing incidence X-ray diffraction.

Abstract Nowadays, green synthesis of nanoparticles using plant precursors has been extensively studied. However, less attention has been given to Mn3O4. This contribution validates the synthesis of single-phase Hausmannite Mn3O4 nanoparticles by a green approach without using any standard acid/base compounds, surfactants, and organic/inorganic dissolving agents. The chemical chelation of the Mn precursor was performed via bioactive compounds of the Aspalathus Linearis’ extract, an African indigenous plant. Annealing at 400 °C for ~ 1 h was required to crystallize the small amorphous nanoparticles with an initial bimodal size distribution peaking at $$\left\langle {\phi_{1} } \right\rangle$$ ϕ 1 ~ 4.21 nm and $$\left\langle {\phi_{2} } \right\rangle$$ ϕ 2 ~ 8.51 nm respectively. Such annealing lead to increase in the diameter of the nanoparticles from 17 to 28 nm.The morphological, structural, vibrational, surface, and photoluminescence properties of the single-phase Hausmannite nanoparticles were comprehensively investigated by High Resolution Transmission Electron Microscopy(HRTEM),Energy Dispersive X-ray Spectroscopy (EDS), X-ray Diffraction (XRD), Raman and X-rays Photoelectron Spectroscopy (XPS), spectroscopy as well as room temperature photoluminescence. Structural and morphological investigations revealed the formation of quasi-spherical nanoparticles having a single phase Hausmannite Mn3O4 crystal structure. XPS results also validated the XRD results about the formation of Hausmannite Mn3O4 nanoparticles. Raman investigations allowed a crystal-clear distinction between the Mn3O4 nature of the nanoparticles from the potential γ -Mn2O3 phase as both phases belong to the same space group and both assume tetragonally-distorted cubic lattices of nearly similar dimensions. The optical studies of the single phase Hausmannite crystalline nanoparticles exhibited a broad photoluminescence in the spectral range of 300–700 nm, which is ideal for emission devices. Graphic abstract

$${\text{Cu}}_{{y}}{\text{Zn}}_{1-2{y}-{x}}{\text{Mn}}_{{y}}/{\text{GO}}$$ (CZMOG) electrodes with y ~ 0.25 and x ~ 0.1 have been fabricated hydrothermally for potential application as a supercapacitive energy-storage electrode. Graphene oxide (GO) is added to the electrodes due to their high surface area and negligible resistance. This synergistic combination of elements of copper (Cu), manganese (Mn), and zinc (Zn) with GO to form CZMOG electrode enhances the latter's performance, stability, and life span. Our results show that the synthesized nanocomposites are crystalline with spherical flake-like shapes. The electrode is then bombarded with Cu ions (Cu2+) irradiation at different doses to determine the effect of Cu2+ irradiation on the performance of the electrodes. Performance evaluation of the electrodes shows that the device characteristics are improved with Cu2+ irradiation, with peak performance observed for samples irradiated with 5.0 × 1015 ions cm−2. Beyond this optimal dosage, the electrode gradually loses its crystallinity with significant electrode damage at a threshold irradiation dose of ~ 1.0 × 1016 ions cm−2. Electrochemical evaluations delivered maximum specific capacitance with cyclic voltammetry (CV) adopting a 10 mVs−1 scan rate and galvanostatic charge discharge (GCD) with 1.0 Ag−1 current density of 1950 and 2556 Fg−1, respectively. Our experimental observations are supported by first-principles density functional theory calculations.

Fuel cell efficiency can be improved by using progressive electrodes and electrolytes. Green nanomaterials and green technologies have been explored for the manufacturing of high-performance electrode and electrolyte materials for fuel cells. Platinum-based electrodes have been replaced with green materials and nanocomposites using green fabrication approaches to attain environmentally friendly fuel cells. In this regard, ecological and sustainable electrode- and electrolyte-based membrane electrode assemblies have also been designed. Moreover, green nanocomposites have been applied to form the fuel cell electrolyte membranes. Among fuel cells, microbial fuel cells have gained research attention for the incorporation of green and sustainable materials. Hence, this review essentially focuses on the potential of green nanocomposites as fuel cell electrode and electrolyte materials and application of green synthesis techniques to attain these materials. The design of and interactions with nanocomposites have led to synergistic effects on the morphology, impedance, resistance, power density, current density, electrochemical features, proton conductivity, and overall efficiency. Moreover, we deliberate the future significance and challenges of the application of green nanocomposites in electrodes and electrolytes to attain efficient fuel cells.

Graphene is one of the most significant carbon nanomaterials, with a one-atom-thick two-dimensional nanostructure. Like other nanocarbons, graphene has been used as a polymer reinforcement. This review explores the impact of graphene and graphene-based nanocomposites on aerospace applications. The fabrication and indispensable features of graphene-derived nanocomposites have been considered. Numerous polymers and nanocomposites have been employed for aerospace systems such as reinforced thermosetting/thermoplastic polymers and epoxy/graphene nanocomposites. Moreover, graphene-modified carbon-fiber-based composites have been discussed for the space sector. Aerospace nanocomposites with graphene have been investigated for superior processability, structural features, morphology, heat stability, mechanical properties, flame resistance, electrical/thermal conductivity, radiation protection, and adhesion applications. Subsequently, epoxy and graphene-derived nanocomposites have been explored for heat/mechanically stable aerospace engineering structures, radiation-shielding materials, adhesives, coatings, etc.

Wide band gap luminescent MoS2 quantum dots (QDs) and MoS2 nanocrystals (NCs) have been synthesized by using laser-assisted chemical vapour deposition and used as an electrode material in supercapacitors. Size-dependent properties of the MoS2 QDs and NCs were examined by UV–vis absorption, photoluminescence, and Raman spectroscopy. The morphological evolution of the NCs and QDs were characterized by using field emission scanning electron microscopy, high-resolution transmission electron microscopy, and atomic force microscopy. The as-synthesized uniform QDs with a size of ∼2 nm exhibited an extended electrochemical potential window of 0.9 V with a specific capacitance value of 255 F/g, while the NCs values were 205 F/g and 0.8 V and the pristine MoS2 with values of 105 F/g and 0.6 V at a scan rate of 1 mV s–1. A shorter conductive pathway and 3D quantum confinement of MoS2 QDs that exhibited a higher number of active sites ensure that the efficient charge storage kinetics along with the intercalation processes at the available edge sites enable significant widening of operating potential window and enhance the capacitance. The symmetric device constructed with the QDs showed a remarkable device capacitance of 50 F/g at a scan rate of 1 mV s–1 with an energy density of ∼5.7 W h kg–1 and achieved an excellent cycle stability of 10,000 consecutive cycles with ∼95% capacitance retention.

In this work, we report a simple and eco-friendly method of synthesizing ZnZrO3 nanocomposites by green approach method using Moringa Oleifera natural plant extract that acted as both capping and reducing agent via their photochemical. The proposed mechanism towards the formation of ZnZrO3 nanocomposites in view of understanding the interaction of Zn (II) and Zr (IV) ions through biological compounds of Moringa Oleifera extract was designed from FTIR analysis. The electrochemical analysis clearly revealed redox peaks at around peak potentials of 0.075 (peak III) and − 0.563 V (peak IV) during the cathodic cycle, due to the reduction and around − 0.252 (peak I) and 0.207 (Peak II), corresponding to the oxidation of ZnZrO3 nanocomposites. The excellent electrochemical performances suggest that ZnZrO3 nanocomposites are highly suitable for electrochemical applications due to good voltammetric response, high electro-activity and good electrochemical kinetics.

Cadmium Oxide nanoparticles have the lowest toxicity when compared to nanoparticles of other semiconductors and they are not detrimental to human and mammalian cells, thereby making them candidates for targeting cancer cells. Synadenium cupulare plant extracts were used to synthesize CdO/CdCO3 nanocomposite using cadmium nitrate tetrahydrate 98% as a precursor salt. The resultant nanoparticles were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy, ultraviolet visible spectroscopy, and Fourier transform infrared spectroscopy (FTIR). The nanoparticles were then screened for effect on breast cancer cell lines (MCF-7 and MDA MB-231) and Vero cell line to determine their growth inhibition effect. Cytotoxicity effect was evaluated using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. XRD showed the peaks of monteponite CdO and otavite CdCO3 nanoparticles. TEM results showed irregular and spherical particles of varying sizes, whilst SEM revealed a non-uniform morphology. FTIR results showed peaks of functional groups which are present in some of the phytochemical compounds found in S. cupulare, and point to the presence of CdO. Annealed CdO/CdCO3 NPs showed selectivity for MCF7 and MDA MB231 in comparison to Vero cell line, thereby supporting the hypothesis that cadmium oxide nanoparticles inhibit growth of cancerous cells more than non-cancerous cells.

Graphene, a single layer graphitic based material, is nowadays the most promising and studied material due to its unique physical and chemical properties [1]. The “top-down” method of synthesizing graphene from graphene oxide (GO) by chemical reduction is the most economical and efficient method. Oxygen based components of GO, such as epoxide, carbonyl, carboxyl and hydroxyl groups have to be eliminated, as much as possible to be more closed to a monomolecular layer of graphite. However, chemical reducing agents, such as hydrazine, are harsh and environmentally unfriendly to be used for large scale production [8]. Madagascar has great varieties of indigenous plants, some of them have a power to heal illness and cancers [16], and used as herbal medicine by traditional health practitioners. This study will complete all reports done on bio-synthesis of graphene by green chemistry process [1]. Hence, physical and optical properties of the obtained graphene sheets mediated by Catharanthus roseus (CR), Phyllarthron madagascariense K. Schum (PM), Cinnamomum camphora cineoliferum (CCC), Cedrelopsis grevei Baill (CGB) and Artemisia annua (AA) natural extracts are reported on this work. Optical and physical properties of the obtained graphene sheets through Raman shift and X-Ray diffraction spectroscopy, confirmed the reduction and conversion of the bulk graphitic material to few-layered reduced graphene oxide. Hence, bio-active compounds extracted from Catharanthus roseus (CR), Phyllarthron madagascariense K. Schum (PM), Cinnamomum camphora cineoliferum (CCC), Cedrelopsis grevei Baill (CGB) and Artemisia annua (AA), can be used and are effective chelating agent for the synthesizing of graphene sheets.

Biosynthesized hematite phase α-Fe2O3 nanoparticles (NPs) have been successfully demonstrated via an entirely green process mediated aqueous extract of Rosmarinus officinalis (rosemary) leaves acting as both stabilizing and capping agents. The synthesis was free of solvents and surfactants to adhere to green chemistry principles and the impartation of environmental benignity. To achieve the goal of this study, the main physical properties of the biosynthesized α-Fe2O3 NPs were carried-out using complementary techniques namely, field emission scanning electron microscopy (FESEM) which revealed the self-assembled, highly agglomerated NPs, and the average size was found to peak at 6.531 ± 0.148 nm while X-ray diffraction (XRD) exhibited several Bragg diffraction peaks in line with the rhombohedral structure and the crystallinity nature of α-Fe2O3 NPs with an average size within the range of 7.412–10.742 nm in agreement with the FESEM results. The energy-dispersive X-ray spectroscopy (EDS) elucidated the presence of Fe and O in addition to contaminating elements from the natural extract while attenuated total reflectance-Fourier transform infrared (ATR-FTIR) depicted Fe-O chemical bonds. Besides, the photoluminescence (PL) emission spectrum indicated the existence of surface defects and oxygen vacancies.

This contribution reports on the thermal conductivity enhancement of MoO3–H2O nano-sheets based nano-fluid. The MoO3–H2O based nano-fluid consists of a set of 2D type nano-sheets with a basal size, approximately ranging from 108 × 200 nm2 to 415 × 631 nm2. A Higher Resolution Transmission Electron Microscopy (HRTEM) observation indicated that the nano-sheets consist of a collection of nano-crystallites (O∼7 nm) with various crystallographic orientations with 15 nm in average diameter. The Molybdenum is mainly in 6+ electronic valence. Their thermal conductivity measured via standard Pt wire exhibited an enhancement of about 36%.

A novel bio- synthesized Ag nanoparticles (AgNPs) using extracts from khat (Catha edulis) plant which is efficient towards mercury ion detection is reported. Ag NPs were characterized by HRTEM, EDS, FTIR/ATR, XRD, UV–Vis absorbance to investigate the size, morphology, chemical bonding, and optical properties, respectively. HRTEM analysis reveals spherical nanoparticles with an average particle size of 14.8 nm. EDS analysis reveals the presence of Ag on the samples and also week signals of Si, Cl, K, Ca, Fe elements originating from the khat plant. According to the FTIR/ATR analysis, we deduce that the phytochemicals in the khat plant are actively involved in the interaction and reduction of the Ag+ ions to Ag. The Brag peaks identified on the XRD spectra are perfectly matched to Face-centered cubic Ag. The Ag NPs recorded a surface Plasmon resonance (SPR) at 450.279 nm which is responsible for the blue colour shift of mercury ion (Hg2+) detection. As a direct application, the sensitivity of Ag NPs was tested towards mercury ions.

Waste management stays a challenge in developing countries. This research reports on the valorisation of agro-waste for the synthesis of nickel oxide nanoparticles (NiO NPs), useful as antibacterial agents to assure the sustainable use of renewable waste resources for human health protection. Agro-waste extracts from Persea americana seed, Zea mays silk and Eucalyptus globulus leaves were used as chelating agents in combination with nickel nitrate to synthesis NiO NPs. Optical, physical and chemical characteristics of synthesised NiO NPs were analysed by Ultraviolet spectroscopy studies (UV–VIS analysis), X-ray powder diffraction (XRD) and Scanning Electron Microscopy (SEM); Fourier Transform Infrared analysis (FTIR) and Energy Dispersive X-Ray Spectroscopy (EDS), respectively. Antibacterial activity of each synthesised NiO-NPs was determined by cell culture in nutrient agar using well diffusion method. The UV–VIS results showed the formation of NiO NPs at wavelength range 300 – 400 nm. The XRD patterns demonstrated the crystalline form of the NiO NPs with a lattice face-centered cubic with average size of 14, 18 and 19 nm for NiO NPs from Persea americana seed, Zea mays silk and Eucalyptus globulus leaves, respectively. SEM images revealed the spherical, pleomorphism and nanosheet surface shape of the synthesised NiO NPs. Chemical elements K, P, Mg, Na, C and O were detected by EDS analysis as forming part of the elemental composition of the NiO NPs synthesised. Chemical bending between O–H, C–H, C–C and C-N was observed using FTIR. Furthermore, antibacterial studies showed the efficacy of all the NiO NPs synthesised against pathogen microbial growth with the largest inhibition zone (IZ) of 26 mm for the NiO NPs from Eucalyptus globulus leaves being observed. Therefore, Eucalyptus globulus leaves are recommended to synthesise NiO NPs for antibacterial applications.

Rock’s hardness is one of the most investigated and important parameters which describes the strength properties of a rock mass. Laser-induced breakdown spectroscopy (LIBS) is a developing spectrochemical elemental analysis technique that is recently investigated to be used for metal hardness measurements. In this work, LIBS has been used to study the surface hardness of selected geological samples. The relationship between sample rebound test hardness, sample density and the LIBS plasma excitation temperature (Te) was investigated. It was observed that there is a linear relationship between the hardness and the density of the samples. Also, it was observed that there is a linear relation between Te and the hardness of the samples. The estimation of the surface hardness of the geological samples by measuring the Te shows the feasibility of LIBS as an easy and reliable method for geological samples’ application.

The REE (rare-earth-elements) cerium (Ce) is the most abundant earth-crust element and their oxides have great attention in the form of nanocrystalline nature with superior physical and chemical properties. Pure and Co (1%, 3% and 5%) doped CeO2 nanoparticles (NPs) synthesized by co-precipitation technique were characterized through X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), UV-visible spectroscopy. XRD shows face-centred-cubic (FCC) crystal symmetry with average crystallite size 6–12nm. HRTEM exhibits almost identical cubical shaped particles with average size 4–10nm. Tuned band-gap may be observed from UV-visible spectrum of CeO2-NPs upon Co (1%, 3% & 5%) incorporation. Enhancement of the photocatalytic activity observed for Co-doped (1%, 3% & 5%) to the degradation of methylene-blue (MB) dye under visible-light absorption.

In the present work, a novel bio-synthesis of highly crystalline cubic MgO nanoparticles from aqueous extracts obtained from date pits is reported. The synthesised cubic MgO nanoparticles were annealed at 500 and 700 °C for 2 h in air. Characterization of the samples was carried out using various characterization techniques. To show the photocatalytic effectiveness of date pits mediated MgO nanoparticles, degradation ability with Methylene blue (MB) under visible irradiation was evaluated. HRTEM analysis of the samples reveals a spherical-like structure of the nanoparticles while selected area electron diffraction and XRD patterns showed that the annealed nanoparticles are crystalline. The photocatalysis efficiency showed 64 and 52% degradation ability for MB of MgO nanoparticles annealed at 500 and 700 °C, respectively.