Indian Institute of Technology Kanpur

The environmental risks posed by traditional oil- and grease-based lubricants can be significantly mitigated by adopting water-based alternatives engineered with superior rheological performance. In this work, we present a fundamentally new and environmentally sustainable aqueous thixotropic colloidal gel of silica nanoparticles formed in the presence of NaCl. We conducted a systematic and detailed investigation of their rheological and tribological characteristics. The tribological performance was evaluated against dry and water-lubricated conditions for steel-steel interface. Our experiments demonstrate that the tribological performance of the formulated nanoparticle gel can be optimized by tuning its rheological properties. A combination of super-low friction and negligible wear was observed. The friction coefficient reduced by up to 97.46% (from 0.63 to 0.016) compared to dry sliding, and by 97.04% (from 0.541 to 0.016) compared to water lubrication. Similarly, the specific wear rate decreased by up to 99.62% and 96.10% under dry conditions and water lubrication respectively. This performance is attributed to a thixotropic, chemically robust gel formed via van der Waals interactions between silica flocs, enabling self-repairing properties, continuous tribo-film formation, and a nano-bearing effect from silica nanoparticles. These attributes enable the gel to maintain and regain its structure during periods of non-shear while also forming a thin film with sufficiently low viscosity to slip into the interfacial contact zone and continuously replenish it with lubricant.

Harmful microorganisms like pathogens significantly impact human health. Meanwhile, industrial growth causes pollution and water contamination by releasing untreated hazardous waste. Effective treatment of these microorganisms and contaminants is essential, and nanocomposites may be a promising solution. The present attempt demonstrates the green synthesis of α-Fe2O3@TiO2 nanocomposites (FTNCs) for the effective treatment of pathogens and organic contaminants.

The FTNCs have been synthesized through a green approach utilizing curcumin extract. Curcumin (Turmeric) extract (TEx) was prepared by washing, drying, and crushing 5 g of turmeric, then boiling it in 100 mL distilled water at 70°C for 1 hour. Metal salts (Fe3+/Ti4+, 2:1) were added to 100 mL of TEx under continuous stirring at 70°C for 24 h. The solution was rinsed and dried at 80°C overnight and heated at 300°C for 3 h to remove impurities.

Synthesized FTNCs have been tested for the potent antibacterial activity against both Gram-positive (Staphylococcus aureus, Bacillus subtilis, Enterococcus faecalis) and Gram-negative bacteria (Escherichia coli, Salmonella Abony, Pseudomonas sp.). Observations discovered noteworthy inhibition of both Gram-positive and Gramnegative bacteria by FTNCs. Furthermore, the FTNCs system shows the energy band gap of ~2.6 eV which may suppress electron recombination, thereby enhancing photocatalysis. The photo-degradation is examined against Evans blue (EB) and Congo red (CR) dyes under UV and visible light (125 W) irradiation. The remarkable photocatalytic degradation efficiency (DE) for CR reached ~67.4% in 60 min.

A simple green approach has been demonstrated for the synthesis of the FTNCs using curcumin-mediated reduction. As prepared FTNCs have been evaluated for potent antibacterial activity against both Gram-positive (Staphylococcus aureus, Bacillus subtilis, Enterococcus faecalis) and Gram-negative bacteria (Escherichia coli, Salmonella Abony, Pseudomonas sp.). The results show that the highest zone of inhibition diameter values have been obtained for 5 mg/mL concertation of FTNCs of ~14, 22,18, 21, and 20 and 29 mm for E. coli, S. abony, S. aureus, B. subtilis, E. faecalis, and Pseudomonas sp., respectively. Additionally, FTNCs demonstrate remarkable photocatalytic degradation efficiency against EB and CR dyes under UV (125 W) irradiation, achieving 56, 67% degradation within 60 min, respectively. The findings indicate that FTNCs show long-term antimicrobial effectiveness and potential for water treatment through photocatalysis. This examination highlights recent advancements in intellectual property rights (IPR) and patent strategies, shedding light on how patents influence eco-friendly synthesis and the development of multifunctional, high-performance nanocomposites.

This study presents an emission inventory for 2022, focusing on assessing the emissions of PM_2.5, PM₁₀, NO_x, SO₂, CO, and VOC from India's road transport, residential, and thermal power sectors. Road transport emissions were estimated using a vehicle kilometer traveled methodology derived from a survey of 200,000 vehicles. A regression analysis was conducted to assess residential fuel usage, considering recent changes in consumption patterns and updated data on cleaner fuels. Estimates for the thermal power sector were based on emission monitoring data. The residential sector is the predominant source of PM_2.5 (1112 kt), PM₁₀ (1678 kt), CO (10630 kt), and VOC (2558 kt). The thermal power sector is the predominant source of secondary air pollutant precursors such as NO_x (2328 kt) and SO₂ (4694 kt). India has the highest emission intensity per gross domestic product (GDP) across sectors compared to other countries. For example, PM_2.5 emissions per GDP from the roads in India are 14, 21, and 10 times that of those in China, the USA, and Europe. The southern (29 %), eastern (30 %), and central (36 %) regions were the notable contributors to emissions from transport, residential, and thermal power sectors. Urban areas contributed 5 % of the total residential sector emissions across India but 25 % of the total road transport sector emissions nationwide. Moreover, power plants within or near the non-attainment cities were responsible for 12 % of the overall thermal power pollution recorded across India. The study identifies unequal emission burdens, with economically disadvantaged regions bearing the brunt.