The facile bio-fabrication of zinc oxide (ZnO) nanoparticles (NPs) is described in this study using an aqueous leaf extract of Salvia officinalis L. as an efficient stabilizing/capping agent. Biosynthesis of nanomaterials using phytochemicals present in the plants has received great attention and is gaining significant importance as a possible alternative to the conventional chemical methods. The properties of the bio-fabricated ZnONPs were examined by different techniques, such as UV-visible spectroscopy, X-ray diffraction spectroscopy (XRD), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermogravimetric/differential scanning calorimetry analysis (TGA/DTG). The photocatalytic activity of ZnONPs was investigated against methyl orange (MO) under UV light irradiation. Under optimum experimental conditions, ZnONPs exhibited 92.47% degradation of MO. Furthermore, the antifungal activity of bio-fabricated ZnONPs was determined against different clinical Candida albicans isolates following standard protocols of broth microdilution and disc diffusion assay. The susceptibility assay revealed that ZnONPs inhibit the growth of all the tested fungal isolates at varying levels with MIC values ranging from 7.81 to 1.95 µg/mL. Insight mechanisms of antifungal action appeared to be originated via inhibition of ergosterol biosynthesis and the disruption of membrane integrity. Thus, it was postulated that bio-fabricated ZnONPs have sustainable applications in developing novel antifungal agents with multiple drug targets. In addition, ZnONPs show efficient photocatalytic efficiency without any significant catalytic loss after the catalyst was recycled and reused multiple times.

Removing organic pollutants, textile dyes, and pharmaceutical wastes from the water bodies has become an essential requirement for a safe environment. Therefore, the present study aimed to prepare semiconductor zinc oxide nanoparticles (ZnO NPs) and plasmonic Ag-supported ZnO nanocomposite (ZnO–Ag) using an environmentally friendly bio-approach as an alternative to hazardous synthesis approaches. ZnO NPs and ZnO–Ag nanocomposite were characterized by using UV–Vis diffuse reflectance spectroscopy (UV–DRS) (the Ag-supported ZnO nanocomposite exhibited an absorption band between 450–550 nm, attributed to the Ag NPs surface plasmon resonance (SPR)), Photoluminescence (PL) spectral investigation, which revealed the PL emission intensity of ZnO–Ag NPs was lower than pure ZnO NPs, describing an extended electron-hole pair (e--h+) lifespan of photogenerated charge carriers, Fourier transform infrared spectroscopy (FTIR), FT-Raman, and X-ray diffraction (XRD) analyses were deduced. In addition, energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) were performed and further ascertained the successful biosynthesis and thermally stable ZnO Nps and ZnO–Ag nanocomposite. The as-prepared ZnO–Ag nanocomposite displayed increased photocatalytic characteristics due to the decline in the bandgap energy from 3.02 eV (ZnO NPs) to 2.90 eV (ZnO–Ag nanocomposite). The photocatalytic activity of the developed nanocomposite for the degradation of methylene blue (MB) dye, a primary textile industry released water-pollutant, was conducted under UV light irradiation. Meanwhile, the maximum % degradation of MB dye molecules was attained by 98.0 % after 60 min exposure of UV-light irradiation. Increased photocatalytic activity of ZnO–Ag nanocomposites and a faster rate of MB degradation were achieved by the deposition of plasmonic Ag NPs and the surface plasmon resonance (SPR) effect possessed by Ag NPs. The primary oxidative route that resulted in MB degradation was the production of hydroxyl radicals (OH^•). The SPR effect of the photocatalyst induced the synergistic enhancement of the optical response and separation of the photo-induced charge carriers. The combined study gives comprehensive information and directions for future research on noble metal-modified nanocatalysts for direct applications in the photocatalytic degradation of textile and organic wastes in water.

Hibiscus sabdariffa is a strongly basic dye with a large number of medicinal applications and is used for various diagnostic purposes. The biofabrication of Fe nanoparticles using Hibiscus sabdariffa (Roselle) flower extract is an eco-friendly and cost-effective protocol reported for the first time in the present investigation. The natural plant extract acts as a non-toxic, biodegradable and economical reducing agent in the biosynthesis of the Fe nanoparticles. Different well-known complementary characterization techniques such as UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), dynamic light scattering (DLS) and thermogravimetric analysis-differential scanning calorimetry (TGA-DSC) were used to investigate the morphological, structural and optical properties of the as-synthesised Fe nanoparticles. The resulting nanoparticles were then utilized as a photocatalyst for the degradation of the toxic organic dye Congo red (CR). UV-visible spectroscopy was used to determine the photocatalytic performance of the Fe nanoparticles under UV irradiation. The results of the photocatalytic degradation of Congo red in aqueous solution under UV light showed a higher photocatalytic activity. A reasonable mechanism was proposed for the enhanced photocatalytic activity of the Fe nanoparticles.

The bio-fabrication of silver nanoparticles (AgNPs) was carried out through the facile green route, using the aqueous extract of Matricaria chamomilla L. Herein, we have developed a cost-efficient, ecofriendly, and photo-induced method for the biomolecule-assisted synthesis of AgNPs using an aqueous extract of Matricaria chamomilla L. as a bio-reducing and capping/stabilizing agent. The biomolecule-capped AgNPs were confirmed from the surface plasmon resonance (SPR) band at λ_max = 450 nm using a UV–visible spectrometer. The stability of the AgNPs was confirmed by recording the UV–visible spectra for a more extended period, and no precipitation was observed in the sol. The morphology and structure of photo-induced biomolecule-capped AgNPs were characterized by different microscopic and spectroscopy techniques such as TEM, SEM, EDX, XRD, and FTIR analysis. The role of phytochemicals as reducing and stabilizing agents was confirmed by comparative FTIR analysis of the AgNPs and pure Matricaria chamomilla L. aqueous extract. The obtained result shows that the AgNPs are mostly spherical morphology with an average size of about 26 nm. Furthermore, the thermal stability of biomolecule-capped AgNPs was examined by TGA-DTG analysis that showed a weight loss of approximately 36.63% up to 800 °C. Moreover, the potential photocatalytic activity of photo-induced AgNPs against Rhodamine B (RB) was examined in the presence of UV light irradiation. The catalyst reusability, the effect of catalyst dosage and initial dye concentration, and the effect of the temperature and pH of the reaction medium were also assessed.

Azoles are generally fungistatic, and resistance to fluconazole is emerging in several fungal pathogens. In an attempt to find novel azole antifungal agents with improved activity, a series of tetrazole ring bearing acylhydrazone derivatives were synthesized and screened for their in vitro antifungal activity. The mechanism of their antifungal activity was assessed by studying their effect on the plasma membrane using flow cytometry and determination of the levels of ergosterol, a fungal-specific sterol. Propidium iodide rapidly penetrated a majority of yeast cells when they were treated with the synthesized compounds at concentrations just above MIC, implying that fungicidal activity resulted from extensive lesions of the plasma membrane. Target compounds also caused a considerable reduction in the amount of ergosterol. The results also showed that the presence and position of different substituents on the phenyl ring of the acylhydrazone pendant seem to play a role on the antifungal activity as well as in deciding the fungistatic and fungicidal nature of the compounds.