Review on green biomass-synthesized metallic nanoparticles and composites and their photocatalytic water purification applications: progress and perspectives

In recent years, the use of biomass for the cost-effective synthesis of nanoparticles has emerged as a promising green technology. Because of their remarkable properties, such as tunable surface plasmon resonance characteristics and high surface areas, bio-synthesised nanomaterials are receiving more scientific and academic attention for their use in various application sectors, especially as catalysts in environmental remediation. Green synthesized nanomaterial's can efficiently contribute to the degradation of a wide range of organic pollutants, including dyes, into harmless by-products. These particles have a cure for recalcitrant organic and inorganic pollutants due to their photocatalytic properties, which largely depend on the production of reactive oxygen species under sunlight or UV illumination. This comprehensive review systematically covers up-to-date knowledge on recent developments in the green synthesis of nanoparticles and composites using plants and microorganisms, unravels underlying mechanisms, and highlights their application areas. It then provides detailed information on their applications in the degradation of potentially toxic organic dyes and the removal of other emerging pollutants, including heavy metals and antibiotics. Finally, the current challenges and perspectives of this technology for future applications are discussed

Reflections on boosting wearable triboelectric nanogenerator performance via interface optimisation

An increasing need to harness power from our surroundings has led researchers to delve into the concept of green energy production from our environment. Textile and wearable triboelectric nanogenerators (t-TENGs or w-TENGs) are a promising option in this regard. Textile and wearable triboelectric nanogenerators can convert mechanical energy present in fabric movements into electrical power using modified textile materials or alternative base materials (such as polyester, PDMS, silicone, etc.). These devices are intended to be mounted on garments or directly on the skin making them highly portable, but could also be installed in any other areas where mechanical energy is present (shoes, floor, bag packs etc.). They have proven to be capable of generating sufficient energy to power some low power devices and sensors. A key present limitation for textile TENGs is their low output compared to non-textile film based TENGs. In this review, we reflect on the task of boosting textile TENG performance via interface modification. Specifically, the paper surveys the improvements that have been possible via surface modification of textiles using different metals or metal oxides and plasma processes. Finally, some key areas are highlighted from a tribology and contact mechanics perspective that may have the potential to lead to further significant enhancements in performance; namely, designing fabric interfaces to boost contact area

Investigating superior performance by configuring bimetallic electrodes on fabric triboelectric nanogenerators (F-TENGs) for IoT enabled touch sensor applications

Fabric Triboelectric Nanogenerators (F-TENGs) are increasingly becoming more significant in wearable monitoring and beyond. These devices offer autonomous energy generation and sensing capabilities, by replacing conventional batteries in flexible wearables. Despite the substantial effort, however, achieving high output with optimal stability, durability, comfort, and washability poses substantial challenges, so we have yet to see any practical commercial uses of these materials. This study focuses on output and investigates the impacts of mono and bimetallic composite fabric electrode configurations on the output performance of F-TENGs. Our findings showcase the superiority of bimetallic configurations, particularly those incorporating Copper (Cu) with Nickel (Ni), over monometallic (Cu only) electrodes. These configurations demonstrate remarkable results, exhibiting a maximum instantaneous voltage, current, and power density of ∼ 199 V (a twofold increase compared to monometallic configurations), ∼22 μA (a threefold increase compared to monometallic configurations), and 2992 mW/m², respectively. Notably, these bimetallic configurations also exhibit exceptional flexibility, shape adaptability, structural integrity, washability, and mechanical stability. Furthermore, the integration of passive component-based power management circuits significantly enhances the performance capabilities of the F-TENGs, highlighting the essential role of power management circuits and electrode selection in optimizing F-TENGs. In addition, we have developed a complete IoT-enabled touch sensor system using CuNi-BEF EcoFlex layered F-TENGs for precise detection of soft and hard touches. This advanced system enhances robotic functionality, enabling nuanced touch understanding essential for precision tasks and fostering more intuitive human-machine interactions

Mechanical energy harvesting and self-powered electronic applications of textile-based piezoelectric nanogenerators: a systematic review

Environmental pollution resulting from fossil fuel consumption and the limited lifespan of batteries has shifted the focus of energy research towards the adoption of green renewable technologies. On the other hand, there is a growing potential for small, wearable, portable electronic devices. Therefore, considering the pollution caused by fossil fuels, the drawbacks of chemical batteries, and the potential applications of small-scale wearables and portable electronic devices, the development of a more effective lightweight power source is essential. In this context, piezoelectric energy harvesting technology has attracted keen attention. Piezoelectric energy harvesting technology is a process that converts mechanical energy into electrical energy and vice-versa. Piezoelectric energy harvesters can be fabricated in various ways, including through solution casting, electrospinning, melt spinning, and solution spinning techniques. Solution and melt-spun filaments can be used to develop woven, knitted, and braided textile-based piezoelectric energy harvesters. The integration of textile-based piezoelectric energy harvesters with conventional textile clothing will be a key enabling technology in realising the next generation smart wearable electronics. This review focuses on the current achievements on textile based piezoelectric nanogenerators (T-PENGs), basic knowledge about piezoelectric materials and the piezoelectric mechanism. Additionally, the basic understanding of textiles, different fabrication methods of T-PENGs, and the strategies to improve the performance of piezoelectric nanogenerators are discussed in the subsequent sections. Finally, the challenges faced in harvesting energy using textile based piezoelectric nanogenerators (T-PENGs) are identified, and a perspective to inspire researchers working in this area is presented

Wearable nanocomposite textile-based piezoelectric and triboelectric nanogenerators: progress and perspectives

In recent years, the widespread adoption of next-generation wearable electronics has been facilitated by the integration of advanced nanogenerator technology with conventional textiles. This integration has led to the development of textile-based nanogenerators (t-NGs), which hold tremendous potential for harvesting mechanical energy from the surrounding environment and serving as power sources for self-powered electronics. Textile structures are inherently flexible, making them well-suited for wearable applications. However, their electrical performance as nanogenerators is significantly limited when used without any modifications. To address this limitation and enhance the electrical performance of textile-based nanogenerators, nanocomposite textiles have been extensively utilized for fabricating advanced nanogenerators. This critical review focuses on the recent progress in wearable nanocomposite textiles-based piezoelectric and triboelectric nanogenerators. The review covers the fundamentals of piezoelectricity and triboelectricity, the working principles of nanogenerators, and the selection of materials. Furthermore, it provides a detailed discussion of nanocomposite textiles in various forms, such as fibers or yarns, fabrics, and electrospun nanofibrous webs, which are employed in piezoelectric and triboelectric nanogenerators. The review also highlights the challenges associated with their implementation and outlines the prospects of textile-based nanogenerators. It can be concluded that nanocomposite textile based piezoelectric and triboelectric nanogenerators exhibit better electrical output and mechanical strength compared to conventional textile based nanogenerators. Nanocomposite electrospun web based piezoelectric nanogenerators exhibit higher piezoelectric output compared with nanocomposite fibre/yarn or fabric based piezoelectric nanogenerators. This is because an in-situ poling takes place in electrospinning unlike with fibre or fabric based piezoelectric nanogenerators. Nanocomposite electrospun web based triboelectric nanogenerators also show better triboelectric output compared to the fibre or fabric-based equivalents. This is due to the higher contact area developed with electrospun nanocomposite webs compared to the fibre or fabric cases. Overall, it can be concluded that while nanocomposite construction can boost output and durability of textile based nanogenerators, more research is required to bring output, stability and durability up to the levels achievable with non-textile based devices

Recent progress in molybdenum disulfide (MoS2) based flexible nanogenerators: an inclusive review

Energy consumption and structure have changed in the new era along with the growth of the Internet of Things (IoT) and artificial intelligence, and the power sources for billions of dispersed gadgets and sensors have sparked attention globally to protect the environment. Due to the rising usage of non-renewable energy sources and the resulting environmental damage, researchers are investigating alternative energy systems that can harness energy from the environment. Therefore, self-sufficient small-scale electronic systems will be possible through the use of underutilised natural waste energy sources collected in nanogenerators (NGs). The features of the materials used have a significant impact on how well NGs work. In this regard Molybdenum disulfide (MoS2), a 2D material, is one of the compounds that is discussed vastly nowadays due to its exceptional characteristics that made it useful in a variety of applications. Many research papers on the advancement and implementation of MoS2 materials have been published, but this article will give an in-depth overview. It offers an introduction and interpretation of the main properties of 2D MoS2 nanomaterials, starting with their current state, properties, and various synthesis processes. Later, the review concentrates on MoS2 applications and energy-harvesting capabilities and gives a comprehensive study of piezoelectric, triboelectric and thermometrical nanogenerators based on 2D MoS2 nanocomposite materials

A critical review on polyvinylidene fluoride (PVDF)/zinc oxide (ZnO) based piezoelectric and triboelectric nanogenerators

In the recent era of energy crisis, piezoelectric and triboelectric effects are surfacing out of several research topics. Polyvinylidene fluoride (PVDF) and its copolymers are well known piezoelectric polymers due to their high piezoelectricity and widely used in flexible devices. PVDF is greatly utilized in preparation of triboelectric layer also due to its higher electronegative nature amongst common polymers. On the other hand, zinc oxide (ZnO) has been studied widely to investigate its multifunctional properties including piezoelectricity, pyroelectricity and antibacterial activity. This versatile material can be prepared, using low cost and environmental friendly routes, in various morphologies. Various research is already performed to capture the synergistic effect of reinforcing ZnO within PVDF polymeric matrix. This work firstly describes the basic principles of piezoelectric and triboelectric effects. Thereafter, piezoelectric and triboelectric performances of PVDF and ZnO based materials are briefly depicted based on their structures. Finally, challenges and future scopes, associated with the mechanical energy harvesting from such materials, are highlighted

Mechanics of Sliding Triboelectric Nanogenerators for Sustainable Energy Harvesting

The triboelectric nanogenerator (TENG) is a new and rapidly advancing energy generation technology that has attracted considerable research interest over the past decade [1,2]. When operated in free-standing mode, TENGs are effective at generating energy in a sustainable manner from low-frequency mechanical motions. TENG offers several advantages over its counterpart generators, most notably their low cost, light weight, easy processing and resistance to corrosion [3,4]. However, conventional TENG devices require precise alignment between functional layers, which is difficult to achieve in a dynamic sliding situation and requires complex arrays of roller bearings, adding frictional losses to the system. In this work, a novel sliding form-factor triboelectric nanogenerator (S-TENG) is proposed which employs compliant parts as a compact, low-cost mechanism to improve alignment between tribo-layers, leading to improved energy harvesting efficiency. The newly designed S-TENG consists of a compliant stator cylinder containing two sets of electrodes, and a mover cylinder with a ring of dielectric material constrained on its outer surface. Relative axial motion between the stator and mover generates a potential difference between the two electrodes via contact electrification and electrostatic induction. The original design utilises a compliant gripping mechanism which ensures conformal contact as TENG output has been found to be very sensitive to real contact area. The S-TENG shows promising electrical output which varies directly with sliding speed and radial force, indicating great potential for use in a variety of energy harvesting applications, including self-powered sensors, and wireless communication devices. Future work will focus on optimizing the mechanical design parameters of the S-TENG and investigating its performance (power output, stability, and durability) under different operating conditions to further enhance its energy harvesting capabilities

Semiconductive Filler-Based Hybrid Piezoelectric Materials

This chapter presents an extensive examination of semiconductive filler-based hybrid piezoelectric materials, with a specific focus on lead-based and lead-free compositions. Lead-based materials, including lead titanate (PbTiO3) and lead zirconate (PbZrO3), undergo modification or are employed in solid solutions to amplify their piezoelectric properties. Techniques such as doping and modification, such as the addition of yttria-stabilized zirconia (YSZ) or Sb2O3, are discussed to enhance the mechanical and electrical characteristics of lead-based ceramics. Moreover, alternative lead-free options, such as potassium sodium niobate (KNN) are explored, with an emphasis on customizing their properties through chemical modifications. Furthermore, the incorporation of semiconductive fillers such as PZT and graphene into piezoelectric matrices is emphasized as a viable strategy for creating nanocomposites with improved piezoelectric properties. These hybrid materials exhibit significant potential for diverse applications in energy-harvesting, structural health monitoring, and related fields.</p