One possible way to reduce the environmental impacts of pesticides is by nanostructuring biocides in nanocarriers because this promotes high and localized biocidal activity and can avoid toxicity to non-target organisms. Neem oil (NO) is a natural pesticide with toxicity concerns to plants, fish, and other organisms. Thus, loading NO in a safe nanocarrier can contribute to minimizing its toxicity. For this study, we have characterized the integrity of a nanosilica-neem oil-based biocide delivery system (SiO₂NP#NO BDS) and evaluated its effectiveness in reducing NO toxicity by the Allium cepa test. NO, mainly consisted of unsaturated fatty acids, was well binded to the SiO₂NP with BTCA crosslinker. Overall, this material presented all of its pores filled with the NO with fatty acid groups at both the surface and bulk level of the nanoparticle. The thermal stability of NO was enhanced after synthesis, and the NO was released as zero-order model with a total of 20 days without burst release. The SiO₂NP#NO BDS was effective in reducing the individual toxicity of NO to the plant system. NO in single form inhibited the seed germination of A. cepa (EC₅₀ of 0.38 g L⁻¹), and the effect was no longer observed at the BDS condition. Contrarily to the literature, the tested NO did not present cyto- and geno-toxic effects in A. cepa, which may relate to the concentration level and composition.

Leaf-cutting ants are important pests of forests and agricultural crops in the Neotropical region. Atta sexdens colonies can be composed of thousands of individuals, which form a highly complex society with a single reproductive queen. Successful control of this species is achieved only if the queen is affected. Few data are available on the lethal or sublethal effects of toxic compounds on leaf-cutting ant queens. Azadirachtin has been claimed as an effective biopesticide for insect control, but its action on leaf-cutting ants has been little explored. This study shows that azadirachtin affects oviposition in A. sexdens queens, impairing egg development by decreasing protein reserves. Azadirachtin inhibits the synthesis of vitellogenin, the major yolk protein precursor. The negative effects of azadirachtin on the reproduction of leaf-cutting ant queens suggest a potential use for the control of these insects.

Biodiesel generated from a variety of non-edible feedstocks has gained widespread acceptance as a limited diesel fuel alternative in compression ignition engines. For the reliable implementation of biodiesel in commercial sectors, its effect on engine combustion, emission, and performance needs to be examined experimentally. In this study, 10% (N10) and 20 % (N20) Neem oil methyl ester (NME) blends were tested in a direct injection 4-stroke single-cylinder diesel engine incorporated with 5% and 10% exhaust gas recirculation (EGR). At maximum load conditions, Brake thermal efficiency (BTE) was found highest for N20 by 7.2%, and also Brake specific energy consumption (BSEC) was reduced by 11.4% for N20 as compared to diesel. Meanwhile, the incorporation of EGR deteriorates the performance parameters for the N20 blend. The results of emission analysis showed that oxides of nitrogen (NOx) increased with the addition of biodiesel whereas the addition of EGR diminished the NOx value for both biodiesel blends at all loading conditions. Unburnt hydrocarbon (UHC), Carbon monoxide (CO), and smoke emissions decreased by 40.6%, 31.2%, and 29.6% for the N20 blend respectively at full load when compared to diesel. Interestingly, when EGR was provided, CO, UHC, and smoke density values are increased for both N10 and N20 blends at all loading conditions, however lower than diesel operation.

The present work details the effects of injection of higher order alcohols, namely hexanol (Hex) and octanol (Oct) as secondary fuels in a CI engine. The last decade has seen an exponential increase in the carbon emission chief of which have been contributed by fossil fuels. Vegetable oils provide a viable alternative to the current scenario as they can be synthesized easily from nature and can be readily adapted for use in CI engines. Neem oil (NO) is non-edible and widely available and hence taken as a base fuel for this research. The poor properties of neem oil were improved by the addition of novel low viscous biofuel, namely wintergreen oil (WGO). During the course of this research work, a blend containing a mixture of 50% of neat neem oil and 50% of wintergreen oil (NO50-WGO50) was optimized based on trial tests and taken as pilot fuel while Hex and Oct were injected along with intake air as secondary fuels. The alcohols were injected into the engine successively in the 10%, 20%, and 30% (by mass) ratios. Experiments were conducted in a single-cylinder CI engine fabricating 5.2-kW power at a constant speed of 1500 rpm at varying load conditions. It is observed that inferior performance of NO led to more smoke, HC, and CO in comparison to diesel at all the loads and these are improved with NO50-WGO50 blend. Nevertheless, a minor increase in NOx emission was perceived with the blend. Addition of higher order alcohol promoted reduction of both NOx and smoke emission without affecting performance. Among the various combinations, NO50-WGO50 + Hex30 and Oct30 reduced NOx emission by 12% and 9.5% and smoke emission by 13% and 19% respectively. These results are on par with the diesel performance and emission characteristics.

In the present study, non-edible seed oil namely raw neem oil was converted into biodiesel using transesterification process. In the experimentation, two biodiesel blends were prepared namely B25 (25% neem oil methyl ester with 75% of diesel) and B50 (50% neem oil methyl ester with 50% diesel). Urea-based selective catalytic reduction (SCR) technique with catalytic converter (CC) was fixed in the exhaust tail pipe of the engine for the reduction of engine exhaust emissions. Initially, the engine was operated with diesel as a working fluid and followed by refilling of biodiesel blends B25 and B50 to obtain the baseline readings without SCR and CC. Then, the same procedure was repeated with SCR and CC technique for emission reduction measurement in diesel, B25 and B50 sample. The experimental results revealed that the B25 blend showed higher break thermal efficiency (BTE) and exhaust gas temperature (EGT) with lower break-specific fuel consumption (BSFC) than B50 blend at all loads. On comparing with biodiesel blends, diesel experiences increased BTE of 31.9% with reduced BSFC of 0.29 kg/kWh at full load. A notable emission reduction was noticed for all test fuels in SCR and CC setup. At full load, B25 showed lower carbon monoxide (CO) of 0.09% volume, hydrocarbon (HC) of 24 ppm, and smoke of 14 HSU and oxides of nitrogen (NOx) of 735 ppm than diesel and B50 in SCR and CC setup. On the whole, the engine with SCR and CC setup showed better performance and emission characteristics than standard engine operation.

The current work focuses on the experimental investigation to analyze the combustion and emission characteristics of a direct injection diesel engine fueled with neat biodiesel (BD100) and different proportions of cyclohexanol blends as a fuel additive in various volume fractions. Cyclohexanol is dispersed into a neat biodiesel in a volume fraction of 10, 20, and 30 vol%. The biodiesel is produced from neem oil by the conventional transesterification process. The experimental results revealed that with the increased cyclohexanol fraction, the combustion was found smooth. The addition of cyclohexanol has a positive influence on various physical and chemical properties of neat biodiesel. The in-cylinder pressure is comparatively low for diesel followed by cyclohexanol and biodiesel blends when compared with neat biodiesel. This is due to shorter ignition delay period. The heat-release rate of neat biodiesel is the highest among all fuels. The overall HC emission of BD70COH30 is 12.19% lower than BD100 and 16.34% lower than diesel. The overall CO₂ emission of BD70COH30 is 13.91% higher than BD100 and 19.5% higher than diesel. The overall NOₓ emission of BD70COH30 is 5.31% lower than BD100 at all load engine operations. The presence of 10, 20, and 30% of cyclohexanol in biodiesel decreased smoke emissions as compared with neat biodiesel and diesel. The overall smoke emission of BD70COH30 is 19.23% lower than BD100 and 25.51% lower than diesel. The overall CO emission of cyclohexanol blended with biodiesel by 30 vol% (BD70COH30) is 17% lower than neat biodiesel and 21.8% lower than diesel. Based on the outcome of this study, neem oil biodiesel and cyclohexanol blends can be employed as a potential alternative fuel for existing unmodified diesel engines owing to its lesser emission characteristics.

Mosquitoes, being a vector for some potentially dreadful diseases, pose a considerable threat to people all around the world. The control over the growth and propagation of mosquitoes comprises conventional pesticides, insect growth regulators and other microbial control agents. However, the usage of these common chemicals and conventional pesticides eventually has a negative impact on human health as well as the environment, which therefore becomes a major concern. The lacuna allows nanotechnology to come into action and exploit nanopesticides. Nanopesticides are majorly divided into two categories—synthetic and biological. Several nanoformulations serve as a promising nanopesticide viz. nanoparticles, e.g. biologically synthesised nanoparticles through plant extracts, nanoemulsions prepared using the essential oils like neem oil and citronella oil and nanoemulsion of conventional pesticides like pyrethroids. These green approaches of synthesising nanopesticides make use of non-toxic and biologically derived compounds and hence are eco-friendly with a better target specificity. Even though there are numerous evidences to show the effectiveness of these nanopesticides, very few efforts have been made to study the possible non-target effects on other organisms prevalent in the aquatic ecosystem. This study focuses on the role of these nanopesticides towards the vector control and its eco-safe property against the other non-target species.

This work investigates the experimental study to examine the operation characteristics of a neat neem oil methyl ester (BD100) along with silver oxide nano-particles as a metal-based additive in various mass fractions. Silver oxide nano-particle is mixed into 100% of BD100 at 5 and 10 ppm. The experimental investigation on diesel engine reveals that the addition of silver oxide nano-particles to BD100 resulted in enhancement of brake thermal efficiency (BTE) with a reduction in brake specific fuel consumption (BSFC). The tested emission parameters such as CO, HC, NOx, and smoke were decreased by 12.22, 10.89, 4.24, and 6.61% for BD100+ Ag₂O (5 ppm) and 16.47, 14.21, 6.66, and 8.34% for BD100 respectively when compared to BD100. Overall, improvement in ignition characteristics of the engine was finer by adding 5 and 10 ppm of silver oxide nano-particle to BD100 on account of the enhanced surface area to volume ratio.

The depletion of fossil fuels and hike in crude oil prices were some of the main reasons to explore new alternatives from renewable source of energy. This work presents the impact of various bowl geometries on diesel engine with diesel and biodiesel samples. Three non-edible oils were selected, namely pumpkin seed oil, orange oil and neem oil. These oils were converted into respective biodiesel using transesterification process in the presence of catalyst and alcohol. After transesterification process, the oils were termed as pumpkin seed oil methyl ester (PSOME), orange oil methyl ester (OME) and neem oil methyl ester (NOME), respectively. The engine used for experimentation was a single-cylinder four-stroke water-cooled direct-injection diesel engine and loads were applied to the engine using eddy current dynamometer. Two bowl geometries were developed, namely toroidal combustion chamber (TCC) and trapezoidal combustion chamber (TRCC). Also, the engine was inbuilt with hemispherical combustion chamber (HCC). The base line readings were recorded using neat diesel fuel with HCC for various loads. Followed by 20% of biodiesel mixed with 80% neat diesel for all prepared methyl esters and termed as B1 (20% PSOME with 80% diesel), B2 (20% OME with 80% diesel) and B3 (20% NOME with 80% diesel). All fuel samples were tested in HCC, TCC and TRCC bowl geometries under standard injection timing and with compression ratio of 18. Increased brake thermal efficiency and reduced brake specific fuel consumption were observed with diesel in TCC geometry. Also, higher heat release and cylinder pressures with lower ignition delay were recorded with TCC bowl geometry. TCC bowl geometry showed lower CO, HC and smoke emissions with B2 fuel sample than diesel and other biodiesel samples. But, higher NOx emission was observed in HCC and TCC than that in TRCC bowl geometry. Graphical abstract ᅟ

The increasing risk of vector-borne diseases and the environmental pollution in the day-to-day life due to the usage of the conventional pesticides makes the role of nanotechnology to come into the action. The current study deals with one of the applications of nanotechnology through the formulation of neem urea nanoemulsion (NUNE). NUNE was formulated using neem oil, Tween 20, and urea using the microfluidization method. Prior to the development of nanoemulsion, the ratio of oil/surfactant/urea was optimized using the response surface modeling method. The mean droplet size of the nanoemulsion was found to be 19.3 ± 1.34 nm. The nanoemulsion was found to be stable for the period of 4 days in the field conditions which aids to its mosquitocidal activity. The nanoemulsion exhibited a potent ovicidal and larvicidal activity against A. aegypti and C. tritaeniorhynchus vectors. This result was corroborated with the histopathological analysis of the NUNE-treated larvae. Further, the effect of NUNE on the biochemical profile of the target host was assessed and was found to be efficacious compared to the bulk counterpart. The nanoemulsion was then checked for its biosafety towards the non-target species like plant beneficial bacterium (E. ludwigii), and phytotoxicity was assessed towards the paddy plant (O. sativa). Nanometric emulsion at the concentration used for the mosquitocidal application was found to be potentially safe towards the environment. Therefore, the nanometric neem-laced urea emulsion tends to be an efficient mosquito control agent with an environmentally benign property.