Photocatalysis and nanoparticles:
1. Bio-mediated route of metal doping: A breakthrough

The main barriers of semiconductor photocatalysts include rapid recombination of photo-generated electron/hole pairs as well as backward reaction, high band gap, and activity only in the UV region. These barriers make the poor activation of the photocatalysts.
Here, we develop a bio-inspired doping technique for the functionalization of semiconductor materials to make them active in the visible light by using the analytes present in biomass without application of external chemical and energy (except stirring). This technique uses the organs of toxic plants, weeds, and leftovers of edible plants such as Thevetia Peruviana, Sphagneticola Trilobata, and Chayote. Such plants are available across the tropical regions and, possess a huge reserve of glycosides, polyphenols, and ascorbic acid. These analytes are first suitably extracted out and then applied for the functionalization of semiconductor supports, namely TiO2 and ZnO using both noble (Ag, Pt etc) and transition (Cu, Ni etc) metals and, the whole process can be carried out a room temperature and atmospheric pressure (Figure 1). The doped catalysts exhibited a dramatic shift of the optical absorption of UV light to the visible domain (450-500 nm) including the solar radiation and, the band gap of TiO2 and ZnO is reduced to a great extent from 3.2 to 2.2 eV and 3.1 to 2.7 eV. The doped catalysts are equally effective for the complete cleavage of emerging pollutants such as pharmaceutically active compounds and typical industrial dyes. The quantum yield (QY) (4.6-5.4%) of TiO2 and ZnO doped catalysts under visible light illumination (17700 Lux) showed a paramount increase (37-44%) in the presence of only solar light (20200 Lux).
The conventional techniques such as thermal and UV photo–reduction have the drawbacks of utilization of harmful chemicals and energy intensive processes. However, the present innovation has the potential to revolutionize the harvesting of solar light for semiconductor photocatalysis for the decontamination of toxic chemicals and, the process is green, simple, efficient, safe, and cost effective.

Figure 1. Pictorial view of steps of present innovation: bio-inspired metal doping on semiconductor supports (here TiO2/ZnO).
2. Metal nanoparticles synthesis and antimicrobial functionalities
1. Electrocatalytic H2O2 formation and sensing
2. Electrocatalytic CO2 conversion to value chemicals
Physiochemical and biochemical processes
1. Heavy metal remediation using functionalized adsorbent and bio-resin
2. Spirulina platensis: A potential scavenger of chromium from wastewater
Advanced oxidation processes (AOPs)
1. Impact of iron chelation on PhACs decomposition in AOPs