Advances in Natural Sciences: Nanoscience and Nanotechnology

In this study UiO-66 and UiO-66-NH₂ were synthesized by solvothermal method. The effect of preparation conditions on the quality of UiO-66-NH₂ was studied. The obtained material has been characterized by x-ray diffraction (XRD), infrared spectroscopy (IR), thermogravimatric analysis (TGA), scanning electron microscopy (SEM) and nitrogen physisorption measurements (BET). The CO₂ and CH₄ physisorption measurements were carried out using a high pressure volumetric analyzer (Micromeritics HPVA—100). The results showed that the UiO-66-NH₂ of ball shape crystalline had been obtained and characterized by high surface area (BET) up to 876 m² g⁻¹, specific volume 0.379 cm³ g⁻¹, pore radius 9.5 Å and thermal stability up to 673 K, respectively. The experiments indicated that in comparison with UiO-66 the addition of NH₂ is able to increase the CO₂ and CH₄ storage capacity at 1 bar and 303 K twice from 28.43 cm³ g⁻¹ up to 52 cm³ g⁻¹ and from 6.68 cm³ g⁻¹ to 11.1 cm³ g⁻¹, respectively.

Copper nanoparticles, due to their interesting properties, low cost preparation and many potential applications in catalysis, cooling fluid or conductive inks, have attracted a lot of interest in recent years. In this study, copper nanoparticles were synthesized through the chemical reduction of copper sulfate with sodium borohydride in water without inert gas protection. In our synthesis route, ascorbic acid (natural vitamin C) was employed as a protective agent to prevent the nascent Cu nanoparticles from oxidation during the synthesis process and in storage. Polyethylene glycol (PEG) was added and worked both as a size controller and as a capping agent. Cu nanoparticles were characterized by Fourier transform infrared (FT-IR) spectroscopy to investigate the coordination between Cu nanoparticles and PEG. Transmission electron microscopy (TEM) and UV–vis spectrometry contributed to the analysis of size and optical properties of the nanoparticles, respectively. The average crystal sizes of the particles at room temperature were less than 10 nm. It was observed that the surface plasmon resonance phenomenon can be controlled during synthesis by varying the reaction time, pH, and relative ratio of copper sulfate to the surfactant. The surface plasmon resonance peak shifts from 561 to 572 nm, while the apparent color changes from red to black, which is partly related to the change in particle size. Upon oxidation, the color of the solution changes from red to violet and ultimately a blue solution appears.

In recent years the outbreak of re-emerging and emerging infectious diseases has been a significant burden on global economies and public health. The growth of population and urbanization along with poor water supply and environmental hygiene are the main reasons for the increase in outbreak of infectious pathogens. Transmission of infectious pathogens to the community has caused outbreaks of diseases such as influenza (A/H₅N₁), diarrhea (Escherichia coli), cholera (Vibrio cholera), etc throughout the world. The comprehensive treatments of environments containing infectious pathogens using advanced disinfectant nanomaterials have been proposed for prevention of the outbreaks. Among these nanomaterials, silver nanoparticles (Ag-NPs) with unique properties of high antimicrobial activity have attracted much interest from scientists and technologists to develop nanosilver-based disinfectant products. This article aims to review the synthesis routes and antimicrobial effects of Ag-NPs against various pathogens including bacteria, fungi and virus. Toxicology considerations of Ag-NPs to humans and ecology are discussed in detail. Some current applications of Ag-NPs in water-, air- and surface- disinfection are described. Finally, future prospects of Ag-NPs for treatment and prevention of currently emerging infections are discussed.

In this study we report on the synthesis of silver nanoparticles (AgNPs) from the leaf extracts of Moringa oleifera using sunlight irradiation as primary source of energy, and its antimicrobial potential. Silver nanoparticle formation was confirmed by surface plasmon resonance at 450 nm and 440 nm, respectively for both fresh and freeze-dried leaf samples. Crystanality of AgNPs was confirmed by transmission electron microscopy, scanning electron microscopy with energy dispersive x-ray spectroscopy and Fourier transform infrared (FTIR) spectroscopy analysis. FTIR spectroscopic analysis suggested that flavones, terpenoids and polysaccharides predominate and are primarily responsible for the reduction and subsequent capping of AgNPs. X-ray diffraction analysis also demonstrated that the size range of AgNPs from both samples exhibited average diameters of 9 and 11 nm, respectively. Silver nanoparticles showed antimicrobial activity on both bacterial and fungal strains. The biosynthesised nanoparticle preparations from M. oleifera leaf extracts exhibit potential for application as broad-spectrum antimicrobial agents.

The colloidal silver solution was synthesized by reducing silver nitrate () using sodium borohydride () and starch as a stabilizer agent. The size and optical properties of synthesized AgNPs were characterized by UV-Vis spectroscopy, Fourier transform-infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The effects of several parameters on AgNPs were also investigated. The results have shown that the size of synthesized spherical silver nanoparticles was and disperse in water. The synthesized AgNPs of his study exhibited a strong antibacterial activity against Gram-negative bacteria Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). The average zones of inhibition of AgNPs were of 7.7 mm for bacteria E. coli and 7.0 mm for S. aureus. In this study, the zone of inhibition of AgNPs was also compared to the reference antibiotics drug.

In this work we have demonstrated a powerful disinfectant ability of colloidal silver nanoparticles (NPs) for the prevention of gastrointestinal bacterial infections. The silver NPs colloid was synthesized by a UV-enhanced chemical precipitation. Two gastrointestinal bacterial strains of Escherichia coli (ATCC 43888-O157:k-:H7) and Vibrio cholerae (O1) were used to verify the antibacterial activity of the as-prepared silver NPs colloid by means of surface disinfection assay in agar plates and turbidity assay in liquid media. Transmission electron microscopy was also employed to analyze the ultrastructural changes of bacterial cells caused by silver NPs. Noticeably, our silver NPs colloid displayed a highly effective bactericidal effect against two tested gastrointestinal bacterial strains at a silver concentration as low as ∼3 mg l⁻¹. More importantly, the silver NPs colloid showed an enhancement of antibacterial activity and long-lasting disinfectant effect as compared to conventional chloramin B (5%) disinfection agent. These advantages of the as-prepared colloidal silver NPs make them very promising for environmental treatments contaminated with gastrointestinal bacteria and other infectious pathogens. Moreover, the powerful disinfectant activity of silver-containing materials can also help in controlling and preventing further outbreak of diseases.

The present article is a review of research works on promising applications of graphene and graphene-based nanostructures. It contains five main scientific subjects. The first one is the research on graphene-based transparent and flexible conductive films for displays and electrodes: efficient method ensuring uniform and controllable deposition of reduced graphene oxide thin films over large areas, large-scale pattern growth of graphene films for stretchble transparent electrodes, utilization of graphene-based transparent conducting films and graphene oxide-based ones in many photonic and optoelectronic devices and equipments such as the window electrodes of inorganic, organic and dye-sensitized solar cells, organic light-emitting diodes, light-emitting electrochemical cells, touch screens, flexible smart windows, graphene-based saturated absorbers in laser cavities for ultrafast generations, graphene-based flexible, transparent heaters in automobile defogging/deicing systems, heatable smart windows, graphene electrodes for high-performance organic field-effect transistors, flexible and transparent acoustic actuators and nanogenerators etc. The second scientific subject is the research on conductive inks for printed electronics to revolutionize the electronic industry by producing cost-effective electronic circuits and sensors in very large quantities: preparing high mobility printable semiconductors, low sintering temperature conducting inks, graphene-based ink by liquid phase exfoliation of graphite in organic solutions, and developing inkjet printing technique for mass production of high-quality graphene patterns with high resolution and for fabricating a variety of good-performance electronic devices, including transparent conductors, embedded resistors, thin-film transistors and micro supercapacitors. The third scientific subject is the research on graphene-based separation membranes: molecular dynamics simulation study on the mechanisms of the transport of molecules, vapors and gases through nanopores in graphene membranes, experimental works investigating selective transport of different molecules through nanopores in single-layer graphene and graphene-based membranes toward the water desalination, chemical mixture separation and gas control. Various applications of graphene in bio-medicine are the contents of the fourth scientific subject of the review. They include the DNA translocations through nanopores in graphene membranes toward the fabrication of devices for genomic screening, in particular DNA sequencing; subnanometre trans-electrode membranes with potential applications to the fabrication of very high resolution, high throughput nanopore-based single-molecule detectors; antibacterial activity of graphene, graphite oxide, graphene oxide and reduced graphene oxide; nanopore sensors for nucleic acid analysis; utilization of graphene multilayers as the gates for sequential release of proteins from surface; utilization of graphene-based electroresponsive scaffolds as implants for on-demand drug delivery etc. The fifth scientific subject of the review is the research on the utilization of graphene in energy storage devices: ternary self-assembly of ordered metal oxide-graphene nanocomposites for electrochemical energy storage; self-assembled graphene/carbon nanotube hybrid films for supercapacitors; carbon-based supercapacitors fabricated by activation of graphene; functionalized graphene sheet-sulfure nanocomposite for using as cathode material in rechargeable lithium batteries; tunable three-dimensional pillared carbon nanotube-graphene networks for high-performance capacitance; fabrications of electrochemical micro-capacitors using thin films of carbon nanotubes and chemically reduced graphenes; laser scribing of high-performance and flexible graphene-based electrochemical capacitors; emergence of next-generation safe batteries featuring graphene-supported Li metal anode with exceptionally high energy or power densities; fabrication of anodes for lithium ion batteries from crumpled graphene-encapsulated Si nanoparticles; liquid-mediated dense integration of graphene materials for compact capacitive energy storage; scalable fabrication of high-power graphene micro-supercapacitors for flexible and on-chip energy storage; superior micro-supercapacitors based on graphene quantum dots; all-graphene core-sheat microfibres for all-solid-state, stretchable fibriform supercapacitors and wearable electronic textiles; micro-supercapacitors with high electrochemical performance based on three-dimensional graphene-carbon nanotube carpets; macroscopic nitrogen-doped graphene hydrogels for ultrafast capacitors; manufacture of scalable ultra-thin and high power density graphene electrochemical capacitor electrodes by aqueous exfoliation and spray deposition; scalable synthesis of hierarchically structured carbon nanotube-graphene fibers for capacitive energy storage; phosphorene-graphene hybrid material as a high-capacity anode material for sodium-ion batteries. Beside above-presented promising applications of graphene and graphene-based nanostructures, other less widespread, but perhaps not less important, applications of graphene and graphene-based nanomaterials, are also briefly discussed.

Electrospinning is a process used to fabricate continuous nanoscale fibers with diameters in the sub-micrometer to nanometer range using a high-voltage power supply. Electrospun (e-spun) fibers and the non-woven webs manufactured from them have attracted considerable attention due to their outstanding characteristics, such as high porosity, small diameter, excellent pore interconnectivity and high surface-to-volume ratio. Because of the useful properties of e-spun fibers, many synthetic and natural polymers, including single and blended polymers, have been electrospun into fibers that can be employed in a variety of applications such as filtration and thermal insulation, and in the manufacture of protective clothing, sensors, conducting devices, wound dressings and scaffolds for tissue engineering. Utilizing the electrospinning technique and its product, some studies on its applications have been conducted in our lab. They included the fabrication of a conducting composite mat for electrical applications, an antibacterial web for a biomedical sector and PCM containing e-spun mat for energy storage.

Nanotechnology has great potential, as it can enhance the quality of life through its applications in various fields like agriculture and the food system. Around the world it has become the future of any nation. But we must be very careful with any new technology to be introduced regarding its possible unforeseen related risks that may come through its positive potential. However, it is also critical for the future of a nation to produce a trained future workforce in nanotechnology. In this process, to inform the public at large about its advantages is the first step; it will result in a tremendous increase in interest and new applications in all the domains will be discovered. With this idea, the present review has been written. There is great potential in nanoscience and technology in the provision of state-of-the-art solutions for various challenges faced by agriculture and society today and in the future. Climate change, urbanization, sustainable use of natural resources and environmental issues like runoff and accumulation of pesticides and fertilizers are the hot issues for today's agriculture. This paper reviews some of the potential applications of nanotechnology in the field of agriculture and recommends many strategies for the advancement of scientific and technological knowledge currently being examined.

The authors report the synthesis of Fe₃O₄ nanoparticles by wet chemical reduction technique at ambient temperature and its characterization. Ferric chloride hexa-hydrate (FeCl₃ · 6H₂O) and sodium boro-hydrate (NaBH₄) were used for synthesis of Fe₃O₄ nanoparticles at ambient temperature. The elemental composition of the synthesized Fe₃O₄ nanoparticles was determined by energy dispersive analysis of x-rays technique. The x-ray diffraction (XRD) technique was used for structural characterization of the nanoparticles. The crystallite size of the nanoparticles was determined using XRD data employing Scherrer's formula and Hall–Williamson's plot. Surface morphology of as-synthesized Fe₃O₄ nanoparticles was studied by scanning electron microscopy. High resolution transmission electron microscopy analysis of the as-synthesized Fe₃O₄ nanoparticles showed narrow range of particles size distribution. The optical absorption of the synthesized Fe₃O₄ nanoparticles was studied by UV–vis–NIR spectroscopy. The as-synthesized nanoparticles were analyzed by Fourier transform infrared spectroscopy technique for absorption band study in the infrared region. The magnetic properties of the as-synthesized Fe₃O₄ nanoparticles were evaluated by vibrating sample magnetometer technique. The thermal stability of the as-synthesized Fe₃O₄ nanoparticles was studied by thermogravimetric technique. The obtained results are elaborated and discussed in details in this paper.

Fe₃O₄/CoFe₂O₄ core/shell nanoparticles with varying shell thickness were fabricated by seed-mediated growth via thermal decomposition method. Ligand exchange process using poly(maleic anhydride-alt-1-octadecene) (PMAO) was performed to prepare the aqueous magnetic fluids from the as-synthesised nanoparticles. X-ray diffraction (XRD), transmission electron microscopy (TEM) and Quantum Design PPMS VersaLab were utilised to characterise morphological and magnetic properties of the sample. XRD results showed that all the particles were single phase with spinel structure and the average crystallite size in the range of 11–17 nm. All particles were spherical in TEM images with similar size compared to results calculated from XRD. Magnetic measurements were performed at different temperatures (50 − 300 K) at 30 kOe. The result showed that the saturation magnetisation (M_s) and coercivity (H_C) were significantly increased with the formation of hard magnetic shell with varying thickness. The dynamic light scattering (DLS) analysis presented a narrow distribution and zeta potential of −16 to −35 mV, indicating a good stability of the ferrofluids. The cytotoxicity of the FOC3/PMAO ferrofluid, which has the highest SAR value of 372.02 W g⁻¹, was tested on Hep-G2 cell line at different concentrations from 10 to 100 μg ml⁻¹. Less than 30% of the cell was inhibited, indicating that the FOC3/PMAO particles have low toxicity at these tested concentrations. Thus, these as-synthesised core/shell nanoparticles with uniform particle size, high saturation magnetisation, good stability and five-time increased specific absorption rate (SAR) compared to the Fe₃O₄ core nanoparticles are very promising in hyperthermia and magnetic resonance imaging (MRI) applications.

Green synthesis of silver nanoparticles (AgNPs) using fruit peel extract has gained considerable interest, as it is an eco-friendly and cost-effective method. However, studies on the use of biosynthesised AgNPs to sterilise plant tissue culture medium as an alternative to autoclaving are limited. Thus, this study presented a biogenic method for synthesising AgNPs using mangosteen peel extract. The biosynthesised AgNPs were characterised by different spectroscopic and microscopic methods, including UV-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and energy dispersive x-ray spectroscopy. The results showed that the phytochemical constituents in the mangosteen peel extract (MPE) helped to reduce Ag⁺ from AgNO₃ to metallic silver (Ag⁰) and stabilise the particles. The formation of biogenic AgNPs was monitored by UV-vis demonstrating a characteristic peak at 425 nm. The AgNPs were spherical and crystalline. The size distribution of the biogenic AgNPs was 5–47 nm with an average diameter of 23.1 ± 6.8 nm. To evaluate the potential of the AgNPs for use as an alternative method to sterilise the culture medium, the antimicrobial activity of the biosynthesised AgNPs (0.1, 1, 10, 100, and 1000 mg l⁻¹) was tested in the banana culture medium. The most feasible concentration of AgNPs to decontaminate the culture medium was 100 mg l⁻¹. Moreover, the results demonstrated that adding 100 mg l⁻¹ AgNPs to the culture medium promoted the growth of the plantlets without any toxic effects. Thus, biogenic AgNPs are a potential biocide to sterilise in vitro banana culture medium.

This study utilised coconut husk biochar as an alternative sustainable carbon support for Pd-based electrocatalyst for ethanol oxidation reaction in basic medium. Coconut husk biochar (BC) was prepared via slow pyrolysis at 800 °C for 1 h at a ramp rate of 5 °C min⁻¹. The Pd/BC catalyst was prepared via borohydride-facilitated reduction of palladium chloride solution. TEM analysis revealed good dispersion of the Pd nanoparticles on the biochar support with particle size ranging from 1.9 to 3.4 nm. Cyclic voltammetry (CV) measurements of Pd/BC in 1.0 M ethanol in 0.1 M KOH gave an on-set potential of −0.615 V (versus Ag/AgCl) with a forward peak current density of 23.87 mA cm⁻², which is slightly higher than the commercial Pd/C catalyst. The Pd/BC also has a higher electrochemical stability and durability than the commercial Pd/C catalyst based on chronoamperometry studies (i.e., 44.43% versus 39.64% current retention). The synthesised coconut husk biochar–supported Pd catalyst exhibited promising results for ethanol oxidation reaction for alkaline direct ethanol fuel cell application.

We describe a simple co-axial electrospinning approach followed by a carbonisation process to create cobalt-carbon (Co-C) nanofibers that are then thoroughly analysed using various techniques. X-ray diffraction measurements showed the creation of pure crystalline cobalt with face-centered cubic (fcc) structure, and average crystallite size was determined using the Debye–Scherrer formula. The average crystallite size has been calculated to be in the range of 10 − 15 nm. According to the Raman investigation, all Co-C nanofibers have an amorphous carbon structure with little graphitic behaviour. Field emission scanning electron microscopy was used to determine the shape and average diameter of electrospun nanofibers. The field-dependent magnetic characterisation demonstrated a satisfactory ferromagnetic behaviour with maximum saturation magnetisation values of 10, 10.2, and 11.2 emu/g for Co12.5-C sample at 300, 100, and 5 K, respectively. Compared to bulk cobalt, the produced Co-C nanofibers have a high coercivity value. With average crystallite size, the coercivity varies. Again, magnetisation versus temperature measurements have supported the existence of ferromagnetism because there is no evidence of blocking temperature or any transitional behaviour below 300 K. As a result, applications for microwave absorption, catalysis, and several magnetic recording devices can benefit from the coupling of ferromagnetic properties with carbon nanofiber materials.

Magnetic particle imaging (MPI) has gained significant traction as an ionising radiation-free tomographic method that offers real-time imaging capabilities with enhanced sensitivity and resolutions. In this technique, magnetic nanoparticles (MNPs) are employed, particularly iron oxide nanoparticles with superparamagnetic nature, as probes within the MPI system. These MNPs enable the tracking and precise quantification of particle movement with minimal background noise. The 3D location and concentration of MNPs can provide better insights for multiple applications in vascular imaging, cell tracking, cancer cell imaging, inflammation, implant monitoring, and trauma imaging and can thus accelerate the diagnosis of disorders. The mononuclear phagocyte system provides a significant advantage, as they are involved in the spontaneous clearance of the tracers used in MPI, which readily minimise the toxic effects. Several studies have demonstrated that MPI-based functional neuroimaging is superior to other imaging modalities, providing adequate temporal resolution images with quick scan intervals. In MPI, nanoparticles are solely responsible for the source and visualisation, unlike magnetic resonance imaging (MRI), where nanoparticles were used only as supportive tracers. This review provides an overview of the principle, diagnostic, and therapeutic applications of MPI as well as the advantages and challenges MPI has over other diagnostic imaging methods in modern clinical setups.

Magnetic particle imaging (MPI) has gained significant traction as an ionising radiation-free tomographic method that offers real-time imaging capabilities with enhanced sensitivity and resolutions. In this technique, magnetic nanoparticles (MNPs) are employed, particularly iron oxide nanoparticles with superparamagnetic nature, as probes within the MPI system. These MNPs enable the tracking and precise quantification of particle movement with minimal background noise. The 3D location and concentration of MNPs can provide better insights for multiple applications in vascular imaging, cell tracking, cancer cell imaging, inflammation, implant monitoring, and trauma imaging and can thus accelerate the diagnosis of disorders. The mononuclear phagocyte system provides a significant advantage, as they are involved in the spontaneous clearance of the tracers used in MPI, which readily minimise the toxic effects. Several studies have demonstrated that MPI-based functional neuroimaging is superior to other imaging modalities, providing adequate temporal resolution images with quick scan intervals. In MPI, nanoparticles are solely responsible for the source and visualisation, unlike magnetic resonance imaging (MRI), where nanoparticles were used only as supportive tracers. This review provides an overview of the principle, diagnostic, and therapeutic applications of MPI as well as the advantages and challenges MPI has over other diagnostic imaging methods in modern clinical setups.

The human gastrointestinal tract is colonised by a multifaceted and dynamic population of microorganisms consisting of trillions of microbes called the gut microbiota. Through extensive research using animal models and human studies, the significant contributions of gut microbiota to immune and metabolic balance, protection against pathogens, and even neurobehavioural traits have been established. Members of the genus Bifidobacterium are the first bacteria to colonise the intestinal tract in infants, and now it has been proven that they play a positive role in enhancing the host immunity, nutrient absorption, reducing and treating gastrointestinal infections, as well as improving conditions such as diarrhea, constipation, and eczema. Bacterial nanotechnology is a rapidly growing research area with great potential for improvement and the discovery of innovations in new applications of bacteria such as Bifidobacterium. In this review, we provide an up-to-date summary of the relations of nanotechnology with Bifidobacterium in various fields, including bacterial synthesis of nanoparticles, encapsulation of bacteria, bacterial toxicity of nanomaterial, application in the field of cancer targeting, and also the treatment of other diseases such as Alzheimer's and IBD.

BNNTs are the tubular variants of the ceramic compound hexagonal boron nitride (hBN) and are known for their high thermal and chemical stability. The research on BNNTs is ever-evolving, researchers are on a quest to optimise the synthesis procedure for the nanomaterial. Here a variety of currently followed synthesis techniques were discussed and compared. X-ray diffraction patterns and electron microscopy results of BNNTs synthesised by various techniques were compared, this would give the pros and cons of each synthesis technique. Based on this, suggestions for the best-suited synthesis technique from an academic as well as industrial perspective were given. The individual properties of these nanotubes, along with their potential applications in the field of spintronics, surface wetting, and radiation capture were delineated.

Biosensors have gained significant attention in various fields such as food processing, agriculture, environmental monitoring, and healthcare. With the continuous advancements in research and technology, a wide variety of biosensors are being developed to cater to diverse applications. However, the effective development of nanobiosensors, particularly the synthesis of nanomaterials, remains a crucial step. Many nanobiosensors face challenges related to instability and selectivity, making it difficult to achieve proper packaging. While some biosensors have been successfully implemented in commercial settings, there is a pressing need to address their limitations and advance their capabilities. The next generation of biosensors, based on nanomaterials, holds promise in overcoming these challenges and enhancing the overall performance of biosensor devices. The commercial viability of these biosensors will rely on their accuracy, reliability, and cost-effectiveness. This review paper provides an overview of various types of nanomaterials and their applications in the development of nanobiosensors. The paper highlights a comparison of different nanomaterial-based biosensors, discussing their advantages, limitations, and performance characteristics.

The photocatalytic activity of nanosized composite materials based on some common metal-oxides has been reviewed in the context of their potential application in the treatment of wastewater. A large volume of published data has been systematically analysed to understand the process of photocatalytic degradation under various combinations of the material, dye and source of excitation. The quantities taken into consideration for the analysis are the average particle size, apparent rate constant (${k}_{obs}$), and maximum percent degradation achieved. Semiconducting titanium dioxide (TiO₂), zinc oxide (ZnO) and copper oxide (CuO) were identified as the three best photocatalysts that can be used after some meticulous modifications, in the treatment of wastewater under visible light irradiation. It was also concluded that the best performance can be obtained with photocatalyst nanoparticles (NPs) of average size in the range of 20 to 70 nm. Among the photocatalysts reviewed, the best degradation was produced by bismuth-sulphur co-doped TiO₂ NPs of around 7 nm average particle size. With a rate constant as high as 6.08 × 10⁻² min⁻¹, this material produced nearly 100% degradation of Indigo Carmine within 40 min under visible light. The ZnO NPs of 40–70 nm average size degraded nearly 99% of Malachite green dye under ultraviolet (UV) irradiations in just 40 min with a very high rate constant of 11.10 × 10⁻² min⁻¹. CuO NPs, synthesised through green methods, produced nearly 95% degradation of Methylene blue (MB) in 2 h, with a rate constant of 2.62 × 10⁻² min⁻¹ under solar irradiation.