Surface Functionalized Mesoporous Silica Nanoparticles for Enhanced Removal of Heavy Metals: A Review

Human health and environmental sustainability are strongly influenced by the contamination of water resources with hazardous heavy metal ions due to the accumulation in human body via food chains. Thereby, researchers’ attention has been paid on effective methods for heavy metal ion scavenging to prevent them releasing to environment. Notably, Mesoporous Silica Nanoparticles (MSNPs) with high surface area, massive surface area to volume ratio, large pore volume and uniform pore distribution play a crucial role in addressing this challenge. Additionally, researchers focus on novel surface functionalization methods of MSNPs with suitable organic and inorganic moieties to amplify the adsorption efficiency of heavy metals. MSNPs possess easily functionalizable surface which facilitates the modifications and enhanced removal of heavy metals. The review article summarizes the different moieties used for functionalization of MSNPs such as amino, thio, carboxyl, phenyl, cyano groups, different types of polymers, inorganic functional groups. Further, a comparison has been made between functional and unmodified MSNPs to elaborate how these modifications have enhanced the removal performance of heavy metals in water. Further, this review provides an overview on different synthesis routes and structure directing agent used in synthesis of MSNPs. Moreover, pH effect on adsorption andreusability of modified NPs, while illustrating the mechanism of adsorption on to modified MSNPs surface has also been elaborated. Maximum adsorption capacity of each functional moiety has been taken into consideration with the aim of supporting future advancements. Keywords: Adsorption, Mesoporous silica nanoparticles, Heavy metals, Functionalization, Maximum adsorption capacit

Application of Metal/Metal Oxide Doped Electrospun Nanofiber Membranes in Sustainable Catalysis

The unsustainability of the production of catalysts due to limited resources and higher energy demands makes it critical to explore and reengineer new catalytic materials for future applications. Woefully, the unrelenting demand for the metals/metal oxides increases both the financial and environmental cost, particularly in mining and synthesis, rendering consumption unsustainable in its current form. In this context, electrospinning offers a new template for designing sustainable ways of minimizing the higher loading of catalysts and recyclability. In this context, metals/metal oxide doped electrospun membranes have grasped a great scientific interest as sustainable catalysts due to their enhanced catalytic activity and synergistic structure-property relationship of the doped material and the matrix. More specifically, the selectivity arising from the electronic properties and quantum mechanical interactions at the nanoscale of metal/metal oxide nanoparticles coupled with interactions at the electrospun membrane interfaces lead to such enhanced properties. This review article summarizes the applications of metals/metal doped electrospun membranes in different aspects of catalysis, such as thermocatalysis, photocatalysis, organocatalysis and electrocatalysis, with a particular focus on their sustainability. Keywords: Sustainable catalysis, metal/metal oxide doped catalysts, electrospinning, organocatalysis, photocatalysi

Potential Applications of Electrospun Nanofibers in Agriculture

Some of the major challenges associated with current agricultural practices include inefficient delivery and utilization of agrochemicals; fertilizers, pesticides, and pheromones; to crops. This results in low nutrient utilization efficiency with respect to applied fertilizers which leads to a greater economic burden to farmers to maintain crop yields at optimum levels. In addition, plant diseases by various pathogens also pose a threat to agriculture. In an effort to address some of the aforementioned challenges, electrospun nanofibers have emerged as a potential class of one-dimensional nanomaterials for use in agricultural applications. Unique characteristics of electrospun nanofibers such as enhanced surface area: volume ratio, high porosity distribution, and increased specific surface area pave the potential for agricultural applications that will be elaborated in this review. These applications include slow-release of fertilizers, pheromones and insecticides, seed and fruit coatings, plant protection, and nanofiber fabricated sensors. In addition, this review also focuses briefly on other preparation methods of nanofibers, and most importantly on the parameters that govern the electrospinning process; solution parameters, processing parameters, and ambient parameters. Furthermore, many more unexplored applications in the field of agriculture employing nanofiber usage exist, and it is believed that a greater understanding of the current nanofiber research and practices of green electrospinning will enable the upliftment of current boundaries to enable agricultural applications of nanofibers on a commercial scale. Keywords: nanofiber - agriculture - electrospinning - slow-release – senso

Climate Smart Agriculture: The Role of Fertilizer Innovations and Efficient Plant Nutrient Management

Climate change has emerged as a significant threat to the global agro-economy, adversely affecting agricultural productivity, food security, and local and global agricultural development goals. To ensure sustainable crop productivity and meet future demands, it is essential to take prompt actions to address the current challenges of lower agricultural productivity due to climate change. Climate-smart agriculture (CSA) is a novel concept that offers a promising approach to tackle these challenges by introducing sustainable farming practices that minimize negative environmental impacts and enhance resilience to climate change. It involves realigning current agricultural practices and introducing smart techniques to reduce the adverse effects of agriculture that contribute to climate change and higher carbon footprints. The importance of climate-smart fertilizers in agricultural productivity cannot be overemphasized, as the soil is susceptible to structural changes and alterations in nutrient availability due to climatic impacts. Therefore, the implementation of proper nutrient management mechanisms and advanced fertilizer innovations has become a top priority in implementing the concepts of CSA. Consequently, there has been a greater focus on introducing more climate-adaptive and resilient plant nutrient delivery systems and technologies in recent times. For instance, nanofertilizer, bio-based controlled-release and slow-release fertilizers have provided a more sustainable and climate-friendly alternative to traditional synthetic fertilizers. Despite the innovations, challenges remain in implementing CSA practices and practices of climate-smart fertilizers at scale. This is largely attributed to the lack of proper knowledge and a streamlined policy framework on climate resilience in agriculture and fertilizers. This article seeks to review the role of fertilizer innovations and nutrient management in CSA, targeting the reduction of nutrient losses due to climate changes. It also examines the current status of climate-smart fertilizers with a particular emphasis on the current implementation challenges and future prospects in fertilizer production, leading to global food security by adapting to climatic changes. By highlighting specific examples of modern climate-smart agriculture and  fertilizer management, this article aims to provide insights into the potential benefits and challenges of implementing CSA practices and encourage further research and development in this important field. Keywords: Climate-smart agriculture, Climate-smart fertilizers, Climate change, Nutrient Management, Innovations in fertilizer

Silica Based Superhydrophobic Nanocoatings for Natural Rubber Surfaces

Silica based nonfluorinated superhydrophobic coatings for natural rubber surfaces have been developed. The coating was synthesized using nanosilica dispersion and a polychloroprene type binder as a compatibilizer. This nanocoating of silica was applied on to the surface of finished natural rubber gloves, by spray coating or dipped coating methods. The nanocoating demonstrates a water contact angle of more than 150° and sliding angle of 7°. The morphological features of the coating have been studied using scanning electron microscopy and atomic force microscopy while Fourier transform infrared spectroscopy was used to understand the nature of surface functional groups. Both imaging techniques provided evidence for the presence of nanosized particles in the coating. Coated gloves demonstrated comparable mechanical properties and significantly better alcohol resistivity when compared to those of the uncoated gloves

Synthesis of Magnetite Nanoparticles by Top-Down Approach from a High Purity Ore

This study attempts to synthesize magnetite nanoparticles from a high purity natural iron oxide ore found in Panvila, Sri Lanka, following a novel top-down approach. Powder X-Ray diffraction, elemental analysis, and chemical analysis data confirmed the ore to be exclusively magnetite with Fe2+ : Fe3+ ratio of 1 : 2. Surface modified magnetite nanoparticles were synthesized by destructuring of this ore using a top-down approach in the presence of oleic acid. These oleic acid coated nanoparticles were further dispersed in ethanol resulting in stable nanomagnetite dispersion. Interestingly, the nanoparticles demonstrated a spherical morphology with a particle size ranging from 20 to 50 nm. Magnetic force microscopic data was used to confirm the topography of the nanoparticles and to study the magnetic domain structure

Urea-Hydroxyapatite Nanohybrids for Slow Release of Nitrogen

While slow release of chemicals has been widely applied for drug delivery, little work has been done on using this general nanotechnology-based principle for delivering nutrients to crops. In developing countries, the cost of fertilizers can be significant and is often the limiting factor for food supply. Thus, it is important to develop technologies that minimize the cost of fertilizers through efficient and targeted delivery. Urea is a rich source of nitrogen and therefore a commonly used fertilizer. We focus our work on the synthesis of environmentally benign nanoparticles carrying urea as the crop nutrient that can be released in a programmed manner for use as a nanofertilizer. In this study, the high solubility of urea molecules has been reduced by incorporating it into a matrix of hydroxyapatite nanoparticles. Hydroxyapatite nanoparticles have been selected due to their excellent biocompatibility while acting as a rich phosphorus source. In addition, the high surface area offered by nanoparticles allows binding of a large amount of urea molecules. The method reported here is simple and scalable, allowing the synthesis of a urea-modified hydroxyapatite nanohybrid as fertilizer having a ratio of urea to hydroxyapatite of 6:1 by weight. Specifically, a nanohybrid suspension was synthesized by $\textit{in situ}$ coating of hydroxyapatite with urea at the nanoscale. In addition to the stabilization imparted due to the high surface area to volume ratio of the nanoparticles, supplementary stabilization leading to high loading of urea was provided by flash drying the suspension to obtain a solid nanohybrid. This nanohybrid with a nitrogen weight of 40% provides a platform for its slow release. Its potential application in agriculture to maintain yield and reduce the amount of urea used is demonstrated.Authors thank Hayleys Agro Ltd., Sri Lanka for initiating this research programme at SLINTEC and Nagarjuna Fertilizer and Chemical Ltd (NFCL), India for providing further support. Authors acknowledge Mr Sunanda Gunesekara of SLINTEC for assistance with scaling up the production process to enable the field trials. ARK acknowledges the financial support received from ICTPELETTRA Users Program, Trieste, Italy to conduct photoemission experiments at Materials Science beam line (MSB) and ELETTRA SRS on HA and urea coated HA samples. ARK further acknowledges Dr. R.G. Acres of MSB beam line for his extensive support to conduct photoemission experiments. We acknowledge the Department of Agriculture and Rice Research and Development Institute of Sri Lanka, in particular Dr Priyantha Weerasinghe, Mr D Sirisena and Dr Amitha Benthota for the assistance in carrying out pot and farmers filed trials. NFCL and Central Salt & Marine Chemicals Research Institute, Gujarat, India for TEM and BET analysis

Urea-Hydroxyapatite Nanohybrids for Slow Release of Nitrogen.

While slow release of chemicals has been widely applied for drug delivery, little work has been done on using this general nanotechnology-based principle for delivering nutrients to crops. In developing countries, the cost of fertilizers can be significant and is often the limiting factor for food supply. Thus, it is important to develop technologies that minimize the cost of fertilizers through efficient and targeted delivery. Urea is a rich source of nitrogen and therefore a commonly used fertilizer. We focus our work on the synthesis of environmentally benign nanoparticles carrying urea as the crop nutrient that can be released in a programmed manner for use as a nanofertilizer. In this study, the high solubility of urea molecules has been reduced by incorporating it into a matrix of hydroxyapatite nanoparticles. Hydroxyapatite nanoparticles have been selected due to their excellent biocompatibility while acting as a rich phosphorus source. In addition, the high surface area offered by nanoparticles allows binding of a large amount of urea molecules. The method reported here is simple and scalable, allowing the synthesis of a urea-modified hydroxyapatite nanohybrid as fertilizer having a ratio of urea to hydroxyapatite of 6:1 by weight. Specifically, a nanohybrid suspension was synthesized by $\textit{in situ}$ coating of hydroxyapatite with urea at the nanoscale. In addition to the stabilization imparted due to the high surface area to volume ratio of the nanoparticles, supplementary stabilization leading to high loading of urea was provided by flash drying the suspension to obtain a solid nanohybrid. This nanohybrid with a nitrogen weight of 40% provides a platform for its slow release. Its potential application in agriculture to maintain yield and reduce the amount of urea used is demonstrated.Authors thank Hayleys Agro Ltd., Sri Lanka for initiating this research programme at SLINTEC and Nagarjuna Fertilizer and Chemical Ltd (NFCL), India for providing further support. Authors acknowledge Mr Sunanda Gunesekara of SLINTEC for assistance with scaling up the production process to enable the field trials. ARK acknowledges the financial support received from ICTPELETTRA Users Program, Trieste, Italy to conduct photoemission experiments at Materials Science beam line (MSB) and ELETTRA SRS on HA and urea coated HA samples. ARK further acknowledges Dr. R.G. Acres of MSB beam line for his extensive support to conduct photoemission experiments. We acknowledge the Department of Agriculture and Rice Research and Development Institute of Sri Lanka, in particular Dr Priyantha Weerasinghe, Mr D Sirisena and Dr Amitha Benthota for the assistance in carrying out pot and farmers filed trials. NFCL and Central Salt & Marine Chemicals Research Institute, Gujarat, India for TEM and BET analysis

Ayurvedic, herbal extracts suppress Candidal biofilms in vitro

Plant derivatives have been used for centuries to treat various human afflictions including microbial infections. A vast majority of these infections are initiated and perpetuated by community dwelling, surface-attached organisms living in micro-econiches known as biofilms. We investigated the biofilm suppressant effect of phytomedicinal preparations used widely in traditional Ayurvedic medicine, Triphala, a mixture of Terminalia bellirica, Terminalia chebula and Emblica officinalis, and Mimusops elengi bark extract. Inhibitory effect of extracts were first investigated against the planktonic C. albicans and C. tropicalis using the well diffusion. Minimum biofilm inhibitory concentration for in-vitro biofilms was determined by MTT assay. The biofilm suppressant effect was determined by measuring biofilm viability at different time intervals, post-exposure to the two herbal extracts, and using MTT. Scanning electron microscopy was performed to assess the post-exposure biofilm architecture. Triphala inhibited both species of the planktonic yeasts, and only the biofilm phase C. tropicalis and mixed species, and not C. albicans. M. elengi had no inhibitory effect on either the planktonic or the biofilms of either Candida species. Ultrastructural microscopy revealed increased cell density of C. albicans biofilm, but not that of C. tropicalis which was significantly reduced in size after Triphala exposure. Triphala, but not M. elengi, extracts exhibit selective and differential biofilm inhibitory activity against Candida. C. albicans biofilms are more resistant to the anti-biofilm activity of Triphala

Two new plant nutrient nanocomposites based on urea coated hydroxyapatite: Efficacy and plant uptake

Macronutrient delivery to plants, particularly nitrogen, is problematic because of losses occurring during fertilization. Currently, nanotechnology is being considered as a solution to improving nutrient use efficiency. In this study, we report the synthesis and plant uptake of two plant nutrient nanocomposites based on urea coated hydroxyapatite (UHA) and potassium encapsulated into (i) a nanoclay, montmorillonite (MMT) or (ii) cavities present in Gliricidia sepium stem resulting in a wood chip containing macronutrients. Soil leaching behaviour, efficacy and plant uptake of the nutrients were tested in a pot experiment using Festuca arundinacea during a period of 60 weeks. Two nanocomposites displayed slow release behaviour particularly for nitrogen, in soil leaching tests compared to the conventional formulations. Both nanoformulations displayed efficient plant nutrient uptake highlighting the improved nutrient use efficiency. These data clearly revealed that urea fabricated into its nanoscale provide platform for development of efficient fertilizer formulations