Development of reliable and eco-accommodating methods for the synthesis of nanoparticles is a vital step in the field of nanotechnology. Silver nanoparticles are important because of their exceptional chemical, physical, and biological properties, and hence applications. In the last decade, numerous efforts were made to develop green methods of synthesis to avoid the hazardous byproducts. This review describes the methods of green synthesis for Ag-NPs and their numerous applications. It also describes the comparison of efficient synthesis methods via green routes over physical and chemical methods, which provide strong evidence for the selection of suitable method for the synthesis of Ag-NPs.

Titanium dioxide (TiO₂) is one of the most widely used photocatalysts due to its physical and chemical properties. In this study, hydrogen energy production using TiO₂- and titanate-based photocatalysts is discussed along with the pros and cons. The mechanism of the photocatalysis has been elaborated to pinpoint the photocatalyst for better performance. The chief characteristics and limitations of the TiO₂ photocatalysts have been assessed. Further, TiO₂-based photocatalysts modified with a transition metal, transition metal oxide, noble metal, graphitic carbon nitride, graphene, etc. have been reviewed. This study will provide a basic understanding to beginners and detailed knowledge to experts in the field to optimize the TiO₂-based photocatalysts for hydrogen production.

Photocatalytic reaction for CO₂reduction in presence of co-catalyst.

Lemon is an essential therapeutic plant of the Rutaceae family having a variety of vital phytochemicals. The TiO₂ nanoparticles (NPs) have been synthesised by the green synthesis method from lemon peel extract for the first time. Hydrolysed extract of lemon peel contains hesperidin flavanol that releases aglycone to act as a capping and reducing agent. The Synthesised samples are characterised through X-rays diffraction spectroscopy (XRD), energy dispersive X-rays spectroscopy (EDX), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and ultraviolet and visible (UV–Vis) spectroscopy techniques. The SEM results depict that the prepared specimen is purely comprised of the agglomerated structures. A close study from TEM exhibits the spherical shape of the particles with the particle size ranges from 80 to 140 nm and anatase form according to the XRD. The Tauc plot prepared from the UV–Vis spectrum shows a bandgap of 3.08 eV. Photocatalytic response of the prepared TiO₂ for the degradation of rhodamine B (RhB) is also studied. The results showed that synthesised particles possess more than 70% photocatalytic activity which is more efficient as compared to commercial TiO₂ particles.